Compiler: Unify all resolved identifier nodes

[SirLynix]

Replaces multiple specific identifier value expression nodes (AliasValueExpression, ConstantExpression, FunctionExpression, etc.) with a single IdentifierValueExpression node.
Add IdentifierType and IdentifierCategory enums for improved identifier handling.

Also move loop unrolling to the LoopUnrollTransformer

[codecov]

Codecov Report

❌ Patch coverage is 78.43666% with 160 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.81%. Comparing base (d248a39) to head (bf98b12).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...NZSL/Ast/Transformations/LoopUnrollTransformer.cpp	83.15%	32 Missing ⚠️
src/NZSL/Ast/IndexRemapperVisitor.cpp	73.04%	31 Missing ⚠️
src/NZSL/Ast/AstSerializer.cpp	23.80%	16 Missing ⚠️
...NZSL/Ast/Transformations/ValidationTransformer.cpp	60.52%	15 Missing ⚠️
src/NZSL/SpirV/SpirvAstVisitor.cpp	48.27%	15 Missing ⚠️
...rc/NZSL/Ast/Transformations/ResolveTransformer.cpp	86.40%	13 Missing and 1 partial ⚠️
include/NZSL/Ast/Nodes.inl	0.00%	9 Missing ⚠️
src/NZSL/GlslWriter.cpp	70.83%	7 Missing ⚠️
src/NZSL/LangWriter.cpp	80.64%	6 Missing ⚠️
...NZSL/Ast/Transformations/LoopUnrollTransformer.inl	57.14%	3 Missing ⚠️
... and 8 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #72      +/-   ##
==========================================
+ Coverage   76.62%   76.81%   +0.18%     
==========================================
  Files         196      198       +2     
  Lines       25139    24809     -330     
  Branches     7751     7721      -30     
==========================================
- Hits        19263    19056     -207     
+ Misses       5775     5650     -125     
- Partials      101      103       +2     

Files with missing lines	Coverage Δ
include/NZSL/Ast/AstSerializer.hpp	100.00% <ø> (ø)
include/NZSL/Ast/Cloner.hpp	100.00% <ø> (ø)
include/NZSL/Ast/Compare.inl	69.14% <100.00%> (+1.28%)	⬆️
include/NZSL/Ast/DependencyCheckerVisitor.hpp	100.00% <ø> (ø)
include/NZSL/Ast/IndexRemapperVisitor.hpp	100.00% <ø> (ø)
include/NZSL/Ast/IndexRemapperVisitor.inl	100.00% <100.00%> (ø)
include/NZSL/Ast/NodeList.hpp	94.73% <100.00%> (+3.43%)	⬆️
include/NZSL/Ast/Nodes.hpp	45.45% <ø> (ø)
include/NZSL/Ast/RecursiveVisitor.hpp	100.00% <ø> (ø)
...Transformations/ConstantPropagationTransformer.hpp	100.00% <ø> (ø)
... and 33 more

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