feat(index): add single-column btree global index build

[QuakeWang]

Purpose

Rust already has BTree global index read support, scan integration, and row-id coverage semantics, but it did not have an entry point to build BTree global index files. This left the Rust read path unable to close the write/read lifecycle by itself.

Brief change log

• Add a single-column BTree global index builder for data-evolution row-tracking append tables.
• Plan index shards by contiguous global row-id ranges and reject missing first_row_id.
• Write BTree index files under {table}/index/ with Java-compatible BTree/index manifest metadata.
• Add Table::new_btree_global_index_build_builder().
• Add CALL sys.create_global_index(..., index_type => 'btree') with unsupported handling for non-BTree types.
• Add tests for shard planning, row-id gaps, missing row ids, overlap rejection, manifest metadata, SQL creation, and fast/full/detail scan behavior after appends.

Tests

• cargo fmt --all -- --check
• cargo clippy --all-targets --workspace --features fulltext,vortex,mosaic -- -D warnings
• cargo test -p paimon btree
• cargo test -p paimon table::global_index_scanner::tests --lib
• cargo test -p paimon table::table_commit::tests::test_global_index --lib
• cargo test -p paimon-datafusion --test procedures

API and Format

Adds a minimal Rust API and SQL procedure for BTree global index creation. The generated files use Java-compatible BTree/index manifest formats.

Documentation