[PWGEM] Use const& and std::move to avoid copies

[vkucera]

Mostly done automatically by Clang-Tidy.

[github-actions]

O2 linter results: ❌ 653 errors, ⚠️ 983 warnings, 🔕 0 disabled

[alibuild]

Error while checking build/O2Physics/code-check for f6fd7c3 at 2026-09-02 22:12:

## sw/BUILD/O2Physics-code-check-latest/log
--
========== List of issues found ==========
++ echo 'Found 173 errors and 302 warnings.'
Found 173 errors and 302 warnings.
++ [[ 173 -gt 0 ]]
++ cat /sw/BUILD/3f2a532f5124f8e8352b439ebf04d58150ae3720/O2Physics-code-check/errors.txt
PWGEM/Dilepton/Core/DielectronCut.h:323:7: error: switch has 2 consecutive identical branches [bugprone-branch-clone,-warnings-as-errors]
PWGEM/Dilepton/Core/DileptonSV.h:122:8: error: constructor does not initialize these fields: ccdb [cppcoreguidelines-pro-type-member-init,-warnings-as-errors]
PWGEM/Dilepton/Core/DileptonSV.h:648:25: error: do not use reinterpret_cast [cppcoreguidelines-pro-type-reinterpret-cast,-warnings-as-errors]
PWGEM/Dilepton/Core/DileptonSV.h:1115:9: error: if with identical then and else branches [bugprone-branch-clone,-warnings-as-errors]
PWGEM/Dilepton/Core/DileptonSV.h:1156:105: error: repeated branch body in conditional chain [bugprone-branch-clone,-warnings-as-errors]
PWGEM/Dilepton/Core/DileptonSV.h:1763:7: error: if with identical then and else branches [bugprone-branch-clone,-warnings-as-errors]
PWGEM/Dilepton/Core/DileptonSV.h:1795:105: error: repeated branch body in conditional chain [bugprone-branch-clone,-warnings-as-errors]
PWGEM/Dilepton/Core/Dilepton.h:110:8: error: constructor does not initialize these fields: ccdb [cppcoreguidelines-pro-type-member-init,-warnings-as-errors]
PWGEM/Dilepton/Core/Dilepton.h:558:25: error: do not use reinterpret_cast [cppcoreguidelines-pro-type-reinterpret-cast,-warnings-as-errors]
PWGEM/Dilepton/Core/Dilepton.h:888:9: error: if with identical then and else branches [bugprone-branch-clone,-warnings-as-errors]
PWGEM/Dilepton/Core/Dilepton.h:914:105: error: repeated branch body in conditional chain [bugprone-branch-clone,-warnings-as-errors]
PWGEM/Dilepton/Core/Dilepton.h:1464:39: error: repeated branch body in conditional chain [bugprone-branch-clone,-warnings-as-errors]
PWGEM/Dilepton/Core/Dilepton.h:1548:7: error: if with identical then and else branches [bugprone-branch-clone,-warnings-as-errors]
PWGEM/Dilepton/Core/Dilepton.h:1566:105: error: repeated branch body in conditional chain [bugprone-branch-clone,-warnings-as-errors]
PWGEM/Dilepton/TableProducer/skimmerPrimaryMuonQC.cxx:60:8: error: constructor does not initialize these fields: ccdb [cppcoreguidelines-pro-type-member-init,-warnings-as-errors]
PWGEM/Dilepton/TableProducer/skimmerPrimaryMuonQC.cxx:176:39: error: do not use static_cast to downcast from a base to a derived class; use dynamic_cast instead [cppcoreguidelines-pro-type-static-cast-downcast,-warnings-as-errors]
PWGEM/Dilepton/TableProducer/skimmerPrimaryMuonQC.cxx:177:24: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGEM/Dilepton/TableProducer/skimmerPrimaryMuon.cxx:66:8: error: constructor does not initialize these fields: ccdb [cppcoreguidelines-pro-type-member-init,-warnings-as-errors]
PWGEM/Dilepton/TableProducer/skimmerPrimaryMuon.cxx:163:39: error: do not use static_cast to downcast from a base to a derived class; use dynamic_cast instead [cppcoreguidelines-pro-type-static-cast-downcast,-warnings-as-errors]
PWGEM/Dilepton/TableProducer/skimmerPrimaryMuon.cxx:164:24: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGEM/Dilepton/TableProducer/skimmerPrimaryMuon.cxx:370:17: error: narrowing conversion from 'float' to 'int' [bugprone-narrowing-conversions,-warnings-as-errors]
PWGEM/Dilepton/Tasks/MCtemplates.cxx:114:8: error: constructor does not initialize these fields: fHistMan, fEventCut [cppcoreguidelines-pro-type-member-init,-warnings-as-errors]
PWGEM/Dilepton/Tasks/MCtemplates.cxx:135:36: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGEM/Dilepton/Tasks/MCtemplates.cxx:135:65: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGEM/Dilepton/Tasks/MCtemplates.cxx:156:51: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGEM/Dilepton/Tasks/MCtemplates.cxx:158:31: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGEM/Dilepton/Tasks/MCtemplates.cxx:160:52: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGEM/Dilepton/Tasks/MCtemplates.cxx:193:8: error: constructor does not initialize these fields: fHistMan [cppcoreguidelines-pro-type-member-init,-warnings-as-errors]
PWGEM/Dilepton/Tasks/MCtemplates.cxx:272:36: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGEM/Dilepton/Tasks/MCtemplates.cxx:272:65: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGEM/Dilepton/Tasks/MCtemplates.cxx:297:59: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGEM/Dilepton/Tasks/MCtemplates.cxx:303:31: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGEM/Dilepton/Tasks/MCtemplates.cxx:306:63: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGEM/Dilepton/Tasks/MCtemplates.cxx:343:71: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGEM/Dilepton/Tasks/MCtemplates.cxx:372:78: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGEM/Dilepton/Tasks/MCtemplates.cxx:419:8: error: constructor does not initialize these fields: fHistMan [cppcoreguidelines-pro-type-member-init,-warnings-as-errors]
PWGEM/Dilepton/Tasks/MCtemplates.cxx:448:34: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGEM/Dilepton/Tasks/MCtemplates.cxx:448:63: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGEM/Dilepton/Tasks/MCtemplates.cxx:564:64: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGEM/Dilepton/Tasks/MCtemplates.cxx:567:83: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGEM/Dilepton/Tasks/MCtemplates.cxx:572:66: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGEM/Dilepton/Tasks/MCtemplates.cxx:575:85: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
[0 more errors; see full log]

Full log here.