Effectively, make GPU compositor available without need to enable
an experimental feature set.
The compositor device is now exposed in the Performance panel of
Render Buttons. It is also still available in the compositor's
N-panel, together with some other options which are more about how
editing works, and not exactly related to render performance.
Pull Request: https://projects.blender.org/blender/blender/pulls/121398
727a90a0f1