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.

core/core_bind.h

@@ -120,7 +120,7 @@ protected:
 public:
 	enum VideoDriver {
 		VIDEO_DRIVER_VULKAN,
-		VIDEO_DRIVER_OPENGL,
+		VIDEO_DRIVER_OPENGL_3,
 	};
 
 	enum Weekday {