feat(file_index): add predicate evaluation foundation

[QuakeWang]

Purpose

Linked issue: #34

The existing FileIndex code can read and write Java-compatible index containers, but it has no internal model for combining index decisions across a Predicate tree. Exposing a reader contract at this stage would also freeze an API that has not yet been validated by a concrete reader.

Brief change log

• Add conservative Remain, Skip, and bitmap-selection results with AND/OR composition.
• Add a crate-private reader seam and recursive predicate evaluator with fail-open behavior and short-circuiting.
• Add tests for result composition, missing or unsupported indexes, nested predicates, and short-circuiting.

Tests

• cargo fmt --all -- --check
• cargo clippy --locked --all-targets --workspace --features fulltext,vortex -- -D warnings
• cargo test --locked -p paimon --all-targets --features fulltext,vortex
• cargo test --locked -p paimon-rest-server --all-targets

API and Format

No public API or storage-format changes.

Documentation

No user-facing documentation changes.