[Tools] Implement --skip-unchanged

[SirLynix]

Implement --skip-unchanged from #74

[codecov]

Codecov Report

❌ Patch coverage is 88.67925% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.91%. Comparing base (ea6e9a6) to head (c928a9a).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/ShaderArchiver/Archiver.cpp	87.50%	0 Missing and 3 partials ⚠️
src/ShaderCompiler/Compiler.cpp	86.95%	0 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #75      +/-   ##
==========================================
- Coverage   81.13%   76.91%   -4.23%     
==========================================
  Files         146      200      +54     
  Lines       18337    24895    +6558     
  Branches        0     7490    +7490     
==========================================
+ Hits        14878    19148    +4270     
- Misses       3459     5631    +2172     
- Partials        0      116     +116     

Files with missing lines	Coverage Δ
src/NZSL/Parser.cpp	88.76% <100.00%> (+0.90%)	⬆️
src/ShaderArchiver/Archiver.hpp	100.00% <ø> (ø)
src/ShaderCompiler/Compiler.hpp	100.00% <ø> (ø)
tests/src/Tests/NzslaTests.cpp	100.00% <100.00%> (ø)
tests/src/Tests/NzslcTests.cpp	96.77% <100.00%> (ø)
src/ShaderArchiver/Archiver.cpp	70.77% <87.50%> (ø)
src/ShaderCompiler/Compiler.cpp	53.42% <86.95%> (ø)

... and 142 files with indirect coverage changes

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