ci/piglit-runner: Merge piglit-driver-*.txt files into driver-*.txt.

The test names are definitely unique (deqp has specific prefixes, piglit
uses '@' as a separator instead of '.'), so we can just have a single file
regardless of test type.  Merges the two groups of xfails together so you
can't mix up which file to edit (I certainly have), and so that we don't
need to introduce yet another set of files when we add gtest for libva.

Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Acked-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Acked-by: Daniel Stone <daniels@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13517>

.gitlab-ci/all-skips.txt

@@ -8,3 +8,10 @@ dEQP-GLES[0-9]*.functional.flush_finish.*
 
 # https://gitlab.freedesktop.org/mesa/mesa/-/issues/4575
 dEQP-VK.wsi.display.get_display_plane_capabilities
+
+# piglit: WGL is Windows-only
+wgl@.*
+
+# These are sensitive to CPU timing, and would need to be run in isolation
+# on the system rather than in parallel with other tests.
+glx@glx_arb_sync_control@timing.*