feat(tests): conditionally include ImGui test engine functionality

- Added conditional compilation for ImGui test engine features in `test_utils.cc` and `test_utils.h`, enabling the loading of ROMs and opening of editors only when the YAZE_ENABLE_IMGUI_TEST_ENGINE flag is set.
- Improved modularity by managing includes based on feature flags, enhancing the flexibility of the testing framework.

Benefits:
- Streamlined testing process for ImGui-related functionalities.
- Enhanced code organization by isolating ImGui test engine dependencies.

test/test_utils.cc

@@ -6,12 +6,16 @@ namespace test {
 namespace gui {
 
 void LoadRomInTest(ImGuiTestContext* ctx, const std::string& rom_path) {
+#ifdef YAZE_ENABLE_IMGUI_TEST_ENGINE
     yaze::core::Controller* controller = (yaze::core::Controller*)ctx->Test->UserData;
     controller->OnEntry(rom_path);
+#endif
 }
 
 void OpenEditorInTest(ImGuiTestContext* ctx, const std::string& editor_name) {
+#ifdef YAZE_ENABLE_IMGUI_TEST_ENGINE
     ctx->MenuClick(absl::StrFormat("Editors/%s", editor_name).c_str());
+#endif
 }
 
 } // namespace gui