Use mimalloc allocator across CLI and Python builds

[benfdking]

Summary

• use mimalloc as the global allocator for all non-wasm CLI builds
• enable mimalloc for the Python extension crate

Testing

• cargo test -p sqruff
• cargo test -p sqruff-cli-python (fails: libpython3.11.so.1.0: cannot open shared object file)

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https://chatgpt.com/codex/tasks/task_e_68b8953015388330a3a18d15e959e10a

[github-actions]

Benchmark for 15f20eb

Click to view benchmark

Test	Base	PR	%
DepthMap::from_parent	60.8±1.25µs	61.2±2.18µs	+0.66%
fix_complex_query	12.1±0.07ms	12.3±0.44ms	+1.65%
fix_superlong	138.5±13.83ms	162.9±15.19ms	+17.62%
parse_complex_query	4.1±0.06µs	4.1±0.03µs	0.00%
parse_expression_recursion	7.1±0.05µs	7.2±0.12µs	+1.41%
parse_simple_query	1033.8±8.97ns	1047.2±48.49ns	+1.30%

[openhands-ai]

Looks like there are a few issues preventing this PR from being merged!

• GitHub Actions are failing:
  • CI

If you'd like me to help, just leave a comment, like

@OpenHands please fix the failing actions on PR #1932 at branch `codex/introduce-mimallocator-to-additional-builds`

Feel free to include any additional details that might help me get this PR into a better state.

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