[common] Never compare null literals when merging range predicates

[LuciferYang]

Purpose

close #9646

Between.optimize merges <= and >= predicates on one field into a BETWEEN, and it ordered the two bounds without checking them:

Object lowerBound = greaterOrEqual.literals().get(0);
Object upperBound = lessOrEqual.literals().get(0);
if (compareLiteral(type, lowerBound, upperBound) >= 0) {

With a null bound that is a NullPointerException from compareTo(null), or RuntimeException("Unsupported type") when the null is the first argument. CALL sys.compact(table => 'db.t', where => 'dt >= 1 AND dt <= null') hits it: procedure filters go through ExpressionHelper.resolveFilter, which runs ConstantFolding but not NullPropagation, so the null literal reaches Paimon intact.

A null bound has no order, so the pair is now left unmerged and evaluated by the rules that already handle this: LeafBinaryFunction.test treats a null literal as no match. Merging into a BETWEEN is an optimization, and skipping it changes nothing semantically.

compareLiteral also gained a guard, since it is the function whose contract was implicit: a null literal now gets an IllegalArgumentException naming the type instead of a NullPointerException from inside compareTo. Its other callers (NotIn, NotBetween, LessThan) either null-check first or are only reached with non-null bounds, so nothing else changes.

I did consider short-circuiting the merge to alwaysFalse(), since k >= 1 AND k <= NULL really does match nothing. I left it out: optimize's job is merging predicates, and having it start producing alwaysFalse reaches past what PredicateBuilder.and asked for, while the evaluation layer already answers false for these.

Tests

BetweenTest.testNullLiteralBoundsDoNotCrash builds k >= 1 AND k <= null through PredicateBuilder.and, asserts it does not throw, and asserts the merged predicate evaluates to false for a row. It also covers a null lower bound and two BETWEENs where one carries a null.

Against the unfixed optimizer the test errors with a NullPointerException.

mvn -pl paimon-common -Dtest=BetweenTest,PredicateTest test on JDK 8: 50 tests, 0 failures. spotless:check and checkstyle:check on paimon-common are clean.