- 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.
Due to the port to Vulkan and complete redesign of the rendering backend,
the `drivers/gles3` code is no longer usable in this state and is not
planned to be ported to the new architecture.
The GLES2 backend is kept (while still disabled and non-working) as it
will eventually be ported to serve as the low-end renderer for Godot 4.0.
Some GLES3 features might be selectively ported to the updated GLES2
backend if there's a need for them, and extensions we can use for that.
So long, OpenGL driver bugs!
As of clang-format 6.0.1, putting the `/* clang-format off */` hint
around our "invalid" `[vertex]` and `[shader]` statements isn't enough
to prevent a bogus indent of the next comments and first valid statement,
so we need to enclose that first valid statement in the unformatted chunk.
