test(Resources): Add comprehensive resource system tests (8 new test files, +48 test cases)

- Add Shader tests (8 test cases)
- Add Material tests (13 test cases)
- Add FileArchive tests (7 test cases)
- Add Loader tests for Texture, Mesh, Audio, Shader, Material (4 tests each)
- Implement IResourceLoader.cpp with ReadFileData and GetExtension
- Update CMakeLists.txt to include new test files and source

engine/CMakeLists.txt

@@ -176,6 +176,7 @@ add_library(XCEngine STATIC
     ${CMAKE_CURRENT_SOURCE_DIR}/src/Resources/ResourceCache.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/src/Resources/AsyncLoader.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/src/Resources/ResourceTypes.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/src/Resources/IResourceLoader.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/src/Resources/Texture.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/src/Resources/Mesh.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/src/Resources/TextureLoader.cpp