Add OpenGL quad integration test with texture mapping

- Add tests/RHI/OpenGL/integration/quad/ with main.cpp, CMakeLists.txt
- Add GLSL shaders (quad.vert, quad.frag) for textured quad rendering
- Use OpenGLVertexArray, OpenGLBuffer, OpenGLShader, OpenGLPipelineState
- Add OpenGLTexture::LoadFromFile for texture loading (earth.png)
- Add OpenGLSampler for texture sampling configuration
- Disable depth test for 2D quad rendering
- GT.ppm generated from OpenGL rendering output (0% diff on re-run)

tests/RHI/OpenGL/integration/quad/Res/Shader/quad.vert

@@ -0,0 +1,11 @@
+#version 460
+
+layout(location = 0) in vec4 aPosition;
+layout(location = 1) in vec2 aTexcoord;
+
+out vec2 vTexcoord;
+
+void main() {
+    gl_Position = aPosition;
+    vTexcoord = aTexcoord;
+}