[codex] Add native token stream parser fast path

[adamziel]

What changed

This stacks on #379.

• Adds WP_MySQL_Native_Token_Stream, a compact Rust token stream returned by WP_MySQL_Native_Lexer::native_token_stream().
• Teaches WP_MySQL_Native_Parser to accept either the existing PHP token array or the native token stream.
• Switches the SQLite driver parser factory to use the native stream when the extension is loaded, with the existing PHP token-array path as the fallback.
• Moves recursive stack-growth checks out of every grammar/node recursion and into the top-level parse/materialization entry points.
• Updates the parser benchmark helper to exercise the stream path when available.

Why

#379 made AST materialization faster, but the driver still created millions of PHP token objects before Rust parsing started. This branch lets Rust parse compact token metadata directly and only materialize PHP-compatible token objects when an AST is requested.

The stack-growth guard was also on the recursive hot path. Keeping the guard at the parse/materialization boundary preserves the stack-growth behavior while removing a large per-rule overhead.

Benchmark

Methodology:

• PHP 8.2 via Nix, release Rust extension build.
• Three generated SQL files, each about 50 MiB, with unique statements.
• Benchmark reads the full file, lexes, parses all statements with next_query(), and calls get_query_ast() for every query.
• PHP baseline is the userland lexer/parser with no extension loaded.
• “Base Rust” is [codex] Speed up native MySQL parser materialization #379 rebuilt/rerun on the same machine.
• “This PR” is this branch with native token streams plus top-level stack checks.

Dataset	Size	Statements	Tokens	PHP total	Base Rust total	This PR total	vs PHP	vs Base Rust	PHP peak	Base Rust peak	This PR peak
long_inserts	52,431,363 B	4,890	9,623,521	157.896s	26.023s	23.104s	6.83x	1.13x	1696.0 MiB	1672.0 MiB	112.0 MiB
edge_selects	52,429,066 B	31,313	11,147,429	149.077s	27.870s	23.526s	6.34x	1.18x	1890.0 MiB	1854.0 MiB	106.0 MiB
mixed_ddl_dml	52,430,929 B	21,482	9,410,229	110.326s	23.008s	18.460s	5.98x	1.25x	1666.0 MiB	1644.0 MiB	108.0 MiB

Validation

• cargo fmt --check
• cargo build --release
• composer run check-cs
• php -d extension=/tmp/mysql-parser-perf/target-stream-release2/release/libwp_mysql_parser.so -d memory_limit=1024M ./vendor/bin/phpunit -c ./phpunit.xml.dist --filter 'MySQL|Parser|Lexer'
• php -d extension=/tmp/mysql-parser-perf/target-stream-release2/release/libwp_mysql_parser.so -d memory_limit=1024M ./vendor/bin/phpunit -c ./phpunit.xml.dist
• php -d memory_limit=1024M ./vendor/bin/phpunit -c ./phpunit.xml.dist --filter 'WP_PDO_MySQL_On_SQLite_PDO_API_Tests::test_query$'