chore(audit): audit predicate expressions across Spark 3.4.3, 3.5.8, 4.0.1, 4.1.1

[andygrove]

Which issue does this PR close?

Closes #.

Rationale for this change

Continuation of the per-category expression audit. Same pattern as #4479 (bitwise), #4478 (map), #4476 (hash), #4475 (conditional), #4474 (misc), #4473 (collection), #4470 (json), #4469 (struct), using the updated audit-comet-expression skill in #4468.

What changes are included in this PR?

Support-doc audit notes

Add per-version audit sub-bullets to all 19 supported predicate SQL function names (!, <, <=, <=>, =, ==, >, >=, and, between, ilike, in, isnan, isnotnull, isnull, like, not, or, rlike).

The Spark expression classes are byte-for-byte identical across the four versions; only the NullIntolerant -> nullIntolerant trait refactor lands in Spark 4.0, with no runtime change. Highlights:

• ! and == are registry aliases for Not and EqualTo.
• between is rewritten by the parser to expr >= low AND expr <= high.
• ilike is RuntimeReplaceable and rewrites to Like(Lower(left), Lower(right)).
• like and rlike cross-reference the existing string-expressions audit (chore(audit): audit string expressions across Spark 3.4.3, 3.5.8, 4.0.1 #4461).
• CometNot already optimizes a few special cases (Not(EqualTo), Not(EqualNullSafe), Not(In)).

Support-level consistency fixes

None. The 12 backing serdes were already clean.

Tracking issues filed for follow-up

None.

Audit process

Audited directly using the audit-comet-expression skill (4 Spark versions per #4468). Twelve serdes, no parallel subagents needed.

How are these changes tested?

• make core succeeds (no code changes; doc only).
• Existing predicate test coverage in CometExpressionSuite and the various SQL-file suites remains unchanged.

[andygrove]

No deferred follow-up work from this audit. The 12 backing serdes in spark/src/main/scala/org/apache/comet/serde/predicates.scala are simple one-line proto wrappers with no shape-restriction withInfo + return None patterns, no Spark 4.0+ collation gaps, no unreachable serde mappings, and no Incompatible markers needing an issue link. like and rlike follow-ups are owned by the string_funcs audit (#4461).