[Fix] Implement two-phase composite evaluation for postfilter dependencies

[Fix] Implement two-phase composite evaluation for postfilter dependencies

Fixes #5674 where composite rules combining postfilter/statistics symbols
with regular filter symbols failed to trigger. Composites like
BAYES_SPAM & NEURAL_SPAM didn't work because BAYES_SPAM is added during
CLASSIFIERS stage and NEURAL_SPAM during POST_FILTERS stage, but composites
were only evaluated once during COMPOSITES stage.

Solution:
- Analyze composite dependencies at configuration time
- Split composites into first-pass (depend only on filters) and second-pass
  (depend on postfilters/stats or other second-pass composites)
- Evaluate first-pass composites during COMPOSITES stage via symcache
- Evaluate second-pass composites during COMPOSITES_POST stage by directly
  iterating the second_pass_composites vector
- Skip symcache checks for second-pass composites during second pass to
  force re-evaluation despite being marked as checked in first pass
- Add functional test demonstrating the fix

The dependency analysis uses transitive closure: if composite A depends on
composite B, and B needs second pass, then A also needs second pass.