[Refactor] (MG_Util/ShaderTranspiler): replace Photon shared vec3 regex hack with SPIR-V pass

Replace the application-specific PackPhotonSharedVec3Memory GLSL regex
patch with a general DecomposeWorkgroupVec3Pass SPIR-V optimization pass.

The new pass decomposes vec3/ivec3/uvec3/bvec3 Workgroup (shared) memory
variables into scalar arrays (e.g. shared vec3 arr[N][M] -> shared float
arr[N][M][3]), rewriting whole-vector loads/stores into per-component
scalar loads/stores. Component-level accesses (e.g. arr[i].x) are
unchanged since a trailing component index into a float[3] yields the
same scalar pointer as it did for a vec3.

Unlike the regex hack, the pass is application-agnostic: it does not
match on variable names, array dimensions, or shader pack identity, and
runs at the SPIR-V level before SPIRV-Cross decompilation.

Registered in SanitizeAndOptimizeBinary after AggressiveDCE so dead
workgroup accesses are already eliminated. Asserts on unsupported
OpAtomic*/OpCopyMemory targeting vec3 workgroup pointers.

Adds ProgramUtilTest.DecomposeWorkgroupVec3InSpirvPass covering array
declaration, +=, whole load/store, component access, and row-copy loop.

CMakeLists.txt

@@ -186,6 +186,7 @@ set(SOURCE_FILES
     MobileGL/MG_Util/ShaderTranspiler/SpirvPasses/FlattenInterfaceStructPass.cpp
     MobileGL/MG_Util/ShaderTranspiler/SpirvPasses/EliminateFloatEqualsZeroPass.cpp
     MobileGL/MG_Util/ShaderTranspiler/SpirvPasses/RenameSamplerFunctionParameterPass.cpp
+    MobileGL/MG_Util/ShaderTranspiler/SpirvPasses/DecomposeWorkgroupVec3Pass.cpp
 
     MobileGL/MG_Util/BackendLoaders/OpenGL/Loader.cpp
     MobileGL/MG_Util/BackendLoaders/Vulkan/Loader.cpp