ci: Enable pre-merge fractional vulkan CTS runs on the turnip driver.

Test 1/50th of the CTS on a630 pre-merge, since we've got hardware that
can do it and infrastructure that should handle instability with a
less-mature driver.

Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5266>
4 files changed