[PWGEM] Implement NUA-weights for flow analysis

[omassen]

Implementing histograms for the determination of Non-uniform acceptance corrections and the application of these weights from the CCDB in the flow analysis.

[github-actions]

O2 linter results: ❌ 132 errors, ⚠️ 222 warnings, 🔕 0 disabled

[alibuild]

Error while checking build/O2Physics/code-check for f107161 at 2026-09-01 17:42:

## sw/BUILD/O2Physics-code-check-latest/log
--
========== List of issues found ==========
++ echo 'Found 12 errors and 19 warnings.'
Found 12 errors and 19 warnings.
++ [[ 12 -gt 0 ]]
++ cat /sw/BUILD/b9f60f9ca2a596b1450f392fe96016fe0d64df50/O2Physics-code-check/errors.txt
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:367:15: error: no header providing "TH3D" is directly included [misc-include-cleaner,-warnings-as-errors]
PWGEM/Dilepton/Core/Dilepton.h:568:25: error: do not use reinterpret_cast [cppcoreguidelines-pro-type-reinterpret-cast,-warnings-as-errors]
PWGEM/Dilepton/Core/Dilepton.h:574:31: error: do not use reinterpret_cast [cppcoreguidelines-pro-type-reinterpret-cast,-warnings-as-errors]
PWGEM/Dilepton/Core/Dilepton.h:576:31: error: do not use reinterpret_cast [cppcoreguidelines-pro-type-reinterpret-cast,-warnings-as-errors]
PWGEM/Dilepton/Core/Dilepton.h:578:31: error: do not use reinterpret_cast [cppcoreguidelines-pro-type-reinterpret-cast,-warnings-as-errors]
PWGEM/Dilepton/Core/Dilepton.h:921:149: error: the const qualified parameter 'weightvector' is copied for each invocation; consider making it a reference [performance-unnecessary-value-param,-warnings-as-errors]
PWGEM/Dilepton/Core/Dilepton.h:925:9: error: if with identical then and else branches [bugprone-branch-clone,-warnings-as-errors]
PWGEM/Dilepton/Core/Dilepton.h:951:105: error: repeated branch body in conditional chain [bugprone-branch-clone,-warnings-as-errors]
PWGEM/Dilepton/Core/Dilepton.h:1507:39: error: repeated branch body in conditional chain [bugprone-branch-clone,-warnings-as-errors]
PWGEM/Dilepton/Core/Dilepton.h:1591:7: error: if with identical then and else branches [bugprone-branch-clone,-warnings-as-errors]
PWGEM/Dilepton/Core/Dilepton.h:1609:105: error: repeated branch body in conditional chain [bugprone-branch-clone,-warnings-as-errors]
++ [[ 19 -gt 0 ]]
++ cat /sw/BUILD/b9f60f9ca2a596b1450f392fe96016fe0d64df50/O2Physics-code-check/warnings.txt
PWGEM/Dilepton/Core/Dilepton.h:88:10: warning: inclusion of deprecated C++ header 'math.h'; consider using 'cmath' instead [modernize-deprecated-headers]
PWGEM/Dilepton/Core/Dilepton.h:348:20: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays]
PWGEM/Dilepton/Core/Dilepton.h:391:7: warning: use auto when initializing with a cast to avoid duplicating the type name [modernize-use-auto]
PWGEM/Dilepton/Core/Dilepton.h:392:7: warning: use auto when initializing with a cast to avoid duplicating the type name [modernize-use-auto]
PWGEM/Dilepton/Core/Dilepton.h:408:7: warning: use auto when initializing with a cast to avoid duplicating the type name [modernize-use-auto]
PWGEM/Dilepton/Core/Dilepton.h:409:7: warning: use auto when initializing with a cast to avoid duplicating the type name [modernize-use-auto]
PWGEM/Dilepton/Core/Dilepton.h:425:7: warning: use auto when initializing with a cast to avoid duplicating the type name [modernize-use-auto]
PWGEM/Dilepton/Core/Dilepton.h:426:7: warning: use auto when initializing with a cast to avoid duplicating the type name [modernize-use-auto]
PWGEM/Dilepton/Core/Dilepton.h:443:7: warning: use auto when initializing with a cast to avoid duplicating the type name [modernize-use-auto]
PWGEM/Dilepton/Core/Dilepton.h:444:7: warning: use auto when initializing with a cast to avoid duplicating the type name [modernize-use-auto]
PWGEM/Dilepton/Core/Dilepton.h:513:39: warning: use nullptr [modernize-use-nullptr]
PWGEM/Dilepton/Core/Dilepton.h:514:43: warning: use nullptr [modernize-use-nullptr]
PWGEM/Dilepton/Core/Dilepton.h:515:24: warning: statement should be inside braces [readability-braces-around-statements]
PWGEM/Dilepton/Core/Dilepton.h:599:11: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays]
PWGEM/Dilepton/Core/Dilepton.h:883:7: warning: do not use 'else' after 'return' [readability-else-after-return]
PWGEM/Dilepton/Core/Dilepton.h:1345:13: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays]
PWGEM/Dilepton/Core/Dilepton.h:1365:13: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays]
PWGEM/Dilepton/Core/Dilepton.h:1480:24: warning: boolean expression can be simplified by DeMorgan's theorem [readability-simplify-boolean-expr]
PWGEM/Dilepton/Core/Dilepton.h:1630:13: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays]
++ [[ 12 -gt 0 ]]
++ exit 1
--

Full log here.