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/linuxbsd/display_server_x11.h

@@ -31,7 +31,7 @@
 #ifndef DISPLAY_SERVER_X11_H
 #define DISPLAY_SERVER_X11_H
 
-#include "drivers/opengl/rasterizer_platforms.h"
+#include "drivers/gles3/rasterizer_platforms.h"
 
 #ifdef X11_ENABLED
 
@@ -48,7 +48,7 @@
 #include "servers/rendering/renderer_compositor.h"
 #include "servers/rendering_server.h"
 
-#if defined(OPENGL_ENABLED)
+#if defined(GLES3_ENABLED)
 #include "gl_manager_x11.h"
 #endif
 
@@ -101,7 +101,7 @@ class DisplayServerX11 : public DisplayServer {
 	Atom requested;
 	int xdnd_version;
 
-#if defined(OPENGL_ENABLED)
+#if defined(GLES3_ENABLED)
 	GLManager_X11 *gl_manager = nullptr;
 #endif
 #if defined(VULKAN_ENABLED)