Previously the device selection was only shown when Blender was started
with the Vulkan backend. However most users don't know that this feature
exists. By also showing the device selection when the backend is changed
in the preferences, will motivate users to revisit the system tab and
see what can be selected.
Another option is to have the device selection fully working even when
running using OpenGL. Technically possible but it requires to mingle Vulkan
with OpenGL data in gpu globals.
Pull Request: https://projects.blender.org/blender/blender/pulls/137646
171f7dcbe7