Optimize logical optimizer: skip map_subqueries + in-place rewriting

[adriangb]

Summary

• map_subqueries short-circuit: skip expression tree walks when no subquery expressions exist (biggest contributor)
• plan_has_subqueries per-pass check: bypass rewrite_with_subqueries entirely when plan has no subqueries
• rewrite_plan_in_place with Arc::make_mut: avoid Arc::unwrap_or_clone + Arc::new cycle during tree traversal
• Adds optimizer-only benchmarks that isolate optimizer perf from SQL parsing/analysis

Benchmark Results (optimizer-only)

Benchmark	Baseline	Optimized	Change
optimizer_select_one_from_700	196 µs	201 µs	+2.7% (noise)
optimizer_select_all_from_1000	4.84 ms	4.25 ms	-12%
optimizer_join_chain_4	150 µs	136 µs	-9%
optimizer_join_chain_8	462 µs	426 µs	-8%
optimizer_wide_filter_200	4.95 ms	3.41 ms	-31%
optimizer_wide_aggregate_100	1.98 ms	1.49 ms	-25%
optimizer_join_4_with_agg_filter	429 µs	358 µs	-17%
optimizer_tpch_all	13.96 ms	11.54 ms	-17%
optimizer_tpcds_all	255.9 ms	213.1 ms	-17%

Test plan

• All 642 optimizer unit tests pass
• Benchmarks confirmed across 2 independent runs
• Run full CI

🤖 Generated with Claude Code