refactor(oxc_str): add IncrementalIdentHasher for byte-by-byte hash computation

[Boshen]

Replace the complex const FxHash implementation with a simpler incremental
hasher that can compute hashes byte-by-byte during lexing.

• Add IncrementalIdentHasher struct with write_byte(), write_bytes(), and finish() methods
• Add Ident::new_with_hash() for creating Idents with precomputed hash
• Simplify compute_hash() const function to use the same incremental algorithm
• Update Ident::new() to use the incremental hasher

Co-Authored-By: Claude Opus 4.5 noreply@anthropic.com

[Boshen]

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• perf(semantic): preserve precomputed identifier hash throughout semantic analysis #18476
• perf(semantic): compute identifier hash incrementally during lexing #18454
• refactor(oxc_str): add IncrementalIdentHasher for byte-by-byte hash computation #18451 👈 (View in Graphite)
• refactor(parser): add cur_ident() for identifiers with precomputed hash #18449
• refactor(semantic): add ArenaIdentHashMap and replace IdentHashMap callsites #18425
• feat(oxc_str): upgrade Ident with precomputed hash for fast equality #18400
• main

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[codspeed-hq]

Merging this PR will not alter performance

✅ 42 untouched benchmarks
⏩ 3 skipped benchmarks¹

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_{Comparing 01-23-refactor_oxc_str_add_incrementalidenthasher_for_byte-by-byte_hash_computation (6d1cc47) with 01-23-refactor_parser_add_cur_ident_for_identifiers_with_precomputed_hash (046b4e6)²}

Footnotes

1. 3 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on 01-23-refactor_parser_add_cur_ident_for_identifiers_with_precomputed_hash (cceaf1e) during the generation of this report, so 9a7c202 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩