We want to run those tests in VKMS later with the same reference image.
To make the tests as close to each other as possible we use the same
resolution for the VKMS and the virtual output which is 640x480.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3350>
This means we can eliminate the use of scattered singletons that isn't
added by the tests or the test framework itself.
tests: Don't get backend from old singleton getter
Either use the ownership chain, or the explicit test context instance
pointer.
tests/wayland: Pass context to test client constructor
So that we can get the Wayland compositor directly from the context.
tests: Don't get display from singleton
tests/client: Make test client carry a context pointer
tests/runner: Have test cases carry a context pointer
tests/wayland/test-driver: Get backend from context
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2718>
Fullscreen Wayland toplevel surfaces don't need to respect the
configured size in which case the window content get centered on a black
background which covers the whole monitor.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2338>