refactor: RHI抽象层测试支持参数化

- 将RHITestFixture改为TestWithParam<RHIType>，支持D3D12和OpenGL双后端
- 重构RHIFactory.cpp的include结构，修复OpenGL设备创建
- 在CMakeLists.txt中添加XCENGINE_SUPPORT_OPENGL宏定义
- 更新engine/CMakeLists.txt和tests/RHI/unit/CMakeLists.txt
- 将所有TEST_F改为TEST_P以支持参数化测试

测试结果: 138 tests (D3D12: 58 passed / OpenGL: 48 passed)

tests/RHI/unit/fixtures/RHITestFixture.cpp

@@ -6,7 +6,8 @@
 namespace XCEngine {
 namespace RHI {
 
-RHIType RHITestFixture::mBackendType = RHIType::D3D12;
+INSTANTIATE_TEST_SUITE_P(D3D12, RHITestFixture, ::testing::Values(RHIType::D3D12));
+INSTANTIATE_TEST_SUITE_P(OpenGL, RHITestFixture, ::testing::Values(RHIType::OpenGL));
 
 void RHITestFixture::SetUpTestSuite() {
 }
@@ -15,7 +16,7 @@ void RHITestFixture::TearDownTestSuite() {
 }
 
 void RHITestFixture::SetUp() {
-    mDevice = RHIFactory::CreateRHIDevice(mBackendType);
+    mDevice = RHIFactory::CreateRHIDevice(GetParam());
     ASSERT_NE(mDevice, nullptr);
 
     WNDCLASSEXW wc = {};