feat(compiler): Generate single emit opcode for negative numbers

[HalidOdat]

A small optimization that replaces the generated output for simple negative numbers, previously emitting StoreInt8 followed by Neg, with a single StoreInt8 instruction that directly emits the negative value.

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	53,125	53,125	0
Passed	51,049	51,049	0
Ignored	1,482	1,482	0
Failed	594	594	0
Panics	0	0	0
Conformance	96.09%	96.09%	0.00%

Tested main commit: 3f8a99641ea51f02dc0ede7fcb75468eb6531bfe
Tested PR commit: 719bb68ef2597f77f34775f7dc4a9d21416a9954
Compare commits: 3f8a996...719bb68

[codecov]

Codecov Report

❌ Patch coverage is 23.07692% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.68%. Comparing base (6ddc2b4) to head (719bb68).
⚠️ Report is 945 commits behind head on main.

Files with missing lines	Patch %	Lines
core/ast/src/expression/literal/mod.rs	0.00%	5 Missing ⚠️
core/engine/src/bytecompiler/expression/unary.rs	37.50%	5 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #5305       +/-   ##
===========================================
+ Coverage   47.24%   59.68%   +12.43%     
===========================================
  Files         476      589      +113     
  Lines       46892    63661    +16769     
===========================================
+ Hits        22154    37994    +15840     
- Misses      24738    25667      +929     

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