feat(c): expose read builder scan options and time-travel through the C binding

[JunRuiLee]

Purpose

The C binding's paimon_table_new_read_builder took only the table — there was no channel to pass a per-read scan selector, so time-travel reads (by snapshot-id / tag / timestamp / version) were unreachable from C.

Brief change log

• Add paimon_table_new_read_builder_with_options(table, options, options_len) taking a paimon_option array. The existing paimon_table_new_read_builder is kept and now delegates to it with an empty map (one shared implementation).
• Resolve time-travel at builder construction: reject more than one time-travel selector up front; run the core's copy_with_time_travel; a selector that is set but does not resolve to a snapshot is an error — never a silent read-of-latest. Unsupported scan options (scan.watermark, incremental) surface as the core's typed error.
• Pin both read-builder symbols with compile-time ABI signature guards.
• Binding-only: no changes to the core crate.

Tests

• cargo test -p paimon-c — empty options build like the plain builder, a non-selector option builds, >1 selector is rejected, an unsupported scan option is rejected, a malformed selector value fails closed (asserting the unified "did not resolve" error), and a null-pointer-with-length guard. Error-path tests assert the error identity, not just the shape.

API and Format

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

Documentation

• Doc comments on the new function.