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

tests/Resources/CMakeLists.txt

@@ -12,6 +12,15 @@ set(RESOURCES_TEST_SOURCES
     test_texture.cpp
     test_mesh.cpp
     test_audio_clip.cpp
+    test_resource_filesystem.cpp
+    test_file_archive.cpp
+    test_shader.cpp
+    test_material.cpp
+    test_texture_loader.cpp
+    test_mesh_loader.cpp
+    test_audio_loader.cpp
+    test_shader_loader.cpp
+    test_material_loader.cpp
 )
 
 add_executable(xcengine_resources_tests ${RESOURCES_TEST_SOURCES})