perf(allocator/vec): remove alloc_guard from RawVec::from_raw_parts_in + clarify safety docs

[overlookmotel]

Follow-on after #10884.

We don't need alloc_guard here. RawVec::from_raw_parts_in is an unsafe method, and caller guarantees that len and capacity are in legal range. We don't need to check the caller fulfilled that guarantee - that responsibility is on them.

Also clarify the safety docs for this method.

[overlookmotel]

• perf(allocator/vec): reduce pointer maths in Vec::extend_desugared #11087
• perf(allocator/vec): Vec::extend_desugared set len only at end #11082
• refactor(allocator/vec): access len and cap fields via getters/setters #11081
• refactor(allocator/vec): re-order methods #11080
• perf(allocator/vec): remove SetLenOnDrop #11079
• refactor(allocator/vec): limit scope of #[expect(clippy::cast_possible_truncation)] #11074
• perf(allocator/vec): remove alloc_guard from RawVec::from_raw_parts_in + clarify safety docs #11073 👈 (View in Graphite)
• docs(allocator/vec): correct safety comments for RawVec::append_elements #11072
• refactor(allocator/vec): clarify comment #11071
• main

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[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #11073 will create unknown performance changes

_{Comparing 05-16-perf_allocator_vec_remove_alloc_guard_from_rawvec_from_raw_parts_in_clarify_safety_docs (7e69c08) with main (fc2f040)}

Summary

🆕 36 new benchmarks

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
🆕	codegen[checker.ts]	N/A	22.3 ms	N/A
🆕	codegen_sourcemap[checker.ts]	N/A	68.9 ms	N/A
🆕	formatter[antd.js]	N/A	714.3 ms	N/A
🆕	formatter[react.development.js]	N/A	8.1 ms	N/A
🆕	formatter[typescript.js]	N/A	1.1 s	N/A
🆕	isolated-declarations[vue-id.ts]	N/A	57 ms	N/A
🆕	lexer[RadixUIAdoptionSection.jsx]	N/A	21.8 µs	N/A
🆕	lexer[antd.js]	N/A	24.7 ms	N/A
🆕	lexer[cal.com.tsx]	N/A	6 ms	N/A
🆕	lexer[checker.ts]	N/A	14.7 ms	N/A
🆕	lexer[pdf.mjs]	N/A	4 ms	N/A
🆕	linter[RadixUIAdoptionSection.jsx]	N/A	2.8 ms	N/A
🆕	linter[cal.com.tsx]	N/A	1.3 s	N/A
🆕	linter[checker.ts]	N/A	3.1 s	N/A
🆕	mangler[antd.js]	N/A	15.7 ms	N/A
🆕	mangler[react.development.js]	N/A	289.2 µs	N/A
🆕	mangler[typescript.js]	N/A	39 ms	N/A
🆕	minifier[antd.js]	N/A	161.2 ms	N/A
🆕	minifier[react.development.js]	N/A	1.8 ms	N/A
🆕	minifier[typescript.js]	N/A	285.6 ms	N/A
...	...	...	...	...

ℹ️ Only the first 20 benchmarks are displayed. Go to the app to view all benchmarks.

[Dunqing]

Yes, the caller must meet safety requirements; otherwise, UB is expected!

[overlookmotel]

Merge activity

• May 17, 6:15 AM EDT: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• May 17, 6:15 AM EDT: overlookmotel added this pull request to the Graphite merge queue.
• May 17, 6:24 AM EDT: Merged by the Graphite merge queue.