Use OpenGL 3.3 core profile instead of compatibility profile

- Rename OpenGL to GLES3 in the source code per community feedback.
  - The renderer is still exposed as "OpenGL 3" to the user.
- Hide renderer selection dropdown until OpenGL support is more mature.
  - The renderer can still be changed in the Project Settings or using
    the `--rendering-driver opengl` command line argument.
- Remove commented out exporter code.
- Remove some OpenGL/DisplayServer-related debugging prints.

platform/uwp/os_uwp.cpp

@@ -175,9 +175,9 @@ Error OS_UWP::initialize(const VideoMode &p_desired, int p_video_driver, int p_a
 	}
 
 	if (opengl_api_type == ContextEGL_UWP::GLES_2_0) {
-		if (RasterizerOpenGLis_viable() == OK) {
-			RasterizerOpenGLregister_config();
-			RasterizerOpenGLmake_current();
+		if (RasterizerGLES3::is_viable() == OK) {
+			RasterizerGLES3::register_config();
+			RasterizerGLES3::make_current();
 		} else {
 			gl_initialization_error = true;
 		}
@@ -319,7 +319,7 @@ void OS_UWP::finalize() {
 
 	rendering_server->finish();
 	memdelete(rendering_server);
-#ifdef OPENGL_ENABLED
+#ifdef GLES3_ENABLED
 	if (gl_context)
 		memdelete(gl_context);
 #endif