[macOS] Improve ANGLE support detection.

Try opening EGL display when checking if ANGLE is supported.

drivers/egl/egl_manager.cpp

@@ -173,6 +173,15 @@ Error EGLManager::_gldisplay_create_context(GLDisplay &p_gldisplay) {
 	return OK;
 }
 
+Error EGLManager::open_display(void *p_display) {
+	int gldisplay_id = _get_gldisplay_id(p_display);
+	if (gldisplay_id < 0) {
+		return ERR_CANT_CREATE;
+	} else {
+		return OK;
+	}
+}
+
 int EGLManager::display_get_native_visual_id(void *p_display) {
 	int gldisplay_id = _get_gldisplay_id(p_display);
 	ERR_FAIL_COND_V(gldisplay_id < 0, ERR_CANT_CREATE);

drivers/egl/egl_manager.h

@@ -92,6 +92,7 @@ private:
 public:
 	int display_get_native_visual_id(void *p_display);
 
+	Error open_display(void *p_display);
 	Error window_create(DisplayServer::WindowID p_window_id, void *p_display, void *p_native_window, int p_width, int p_height);
 
 	void window_destroy(DisplayServer::WindowID p_window_id);

platform/macos/display_server_macos.mm

@@ -4501,7 +4501,7 @@ DisplayServerMacOS::DisplayServerMacOS(const String &p_rendering_driver, WindowM
 #if defined(GLES3_ENABLED)
 	if (rendering_driver == "opengl3_angle") {
 		gl_manager_angle = memnew(GLManagerANGLE_MacOS);
-		if (gl_manager_angle->initialize() != OK) {
+		if (gl_manager_angle->initialize() != OK || gl_manager_angle->open_display(nullptr) != OK) {
 			memdelete(gl_manager_angle);
 			gl_manager_angle = nullptr;
 			bool fallback = GLOBAL_GET("rendering/gl_compatibility/fallback_to_native");