feat(c): expose string and range predicates through the C binding

[JunRuiLee]

Purpose

The C binding (bindings/c) exposed only comparison, null, and IN/NOT IN predicates. String-pattern and range operators — already implemented in the core PredicateBuilder — were unreachable from C, so C consumers (e.g. engine integrations) could not push those filters down.

Brief change log

• Add C FFI functions for starts_with / ends_with / contains / like / between / not_between, each with a default (case-sensitive) and a _with_case_sensitive variant.
• Reuse the existing build_leaf_predicate_datum / build_leaf_predicate_datums helpers; like maps its escape byte via a small escape_char_from_c helper (0 → core default \) and passes it through a closure, so no error-handling path is duplicated. Non-\ escapes are rejected by core.
• Pin the six new base symbols with compile-time signature assertions, matching the existing convention that guards C-linked predicate symbols against accidental ABI changes.
• Binding-only: no changes to the core crate.

Tests

• cargo test -p paimon-c — added unit tests covering the happy path, a rejected non-\ escape, a non-string datum error, the low > high short-circuit, and a smoke test touching every _with_case_sensitive variant.

API and Format

• Adds new C API symbols; no change to existing symbols or to any storage format.

Documentation

• Doc comments on each new function; no separate docs needed.

[JingsongLi]

+1