Refactor/lexer hex optimization ,#5108

[MayankRaj435]

Optimize hex escape parsing in lexer

This Pull Request fixes/closes #5108.

It changes the following:

• Performance Optimization: Refactored take_unicode_escape_sequence and take_hex_escape_sequence in core/parser/src/lexer/string.rs to parse hexadecimal digits directly from the character stream into a u32 accumulator.
• Allocation Removal: Eliminated unnecessary heap allocations (Vec<u32> and String) that were previously used as buffers for u32::from_str_radix and u16::from_str_radix.
• Code Cleanup: Removed the take_until method from core/parser/src/lexer/cursor.rs as it is no longer used by the optimized escape sequence parsing.
• Lint Fixes: Cleaned up unused imports in core/parser/src/lexer/cursor.rs discovered after the refactoring.

Verification Results:

• Lexer Tests: All 63 tests in core/parser/src/lexer/tests.rs passed successfully.
• Parser Tests: Verified broader compatibility by running the full boa_parser test suite.
• Style/Linting: Passed both cargo fmt and cargo clippy -- -D warnings without any issues.

[MayankRaj435]

@jedel1043 @nekevss Please review it once at your convenience ,thanks

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	52,963	52,963	0
Passed	50,073	50,073	0
Ignored	2,072	2,072	0
Failed	818	818	0
Panics	0	0	0
Conformance	94.54%	94.54%	0.00%

Tested main commit: daf86d30277a5c1fb353825347f75c1d83516905
Tested PR commit: 82dece19c7b7132d5e7ab480ddf3d1e6d59e301e
Compare commits: daf86d3...82dece1

[codecov]

Codecov Report

❌ Patch coverage is 72.97297% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.58%. Comparing base (6ddc2b4) to head (de661fc).
⚠️ Report is 921 commits behind head on main.

Files with missing lines	Patch %	Lines
core/parser/src/lexer/string.rs	72.97%	10 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #5109       +/-   ##
===========================================
+ Coverage   47.24%   59.58%   +12.33%     
===========================================
  Files         476      589      +113     
  Lines       46892    63449    +16557     
===========================================
+ Hits        22154    37804    +15650     
- Misses      24738    25645      +907     

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[jedel1043]

Unrelated change from another PR

[MayankRaj435]

fixed those ,please review it .Thanks

[MayankRaj435]

@jedel1043 I think it can be merged now?

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	52,963	52,963	0
Passed	50,732	50,732	0
Ignored	1,426	1,426	0
Failed	805	805	0
Panics	0	0	0
Conformance	95.79%	95.79%	0.00%

Tested main commit: f075094f9674f9919b4d2e85ca1bcba410bf34b0
Tested PR commit: de661fc3a0d39f49cb272a0f013b7b66ed380bdf
Compare commits: f075094...de661fc