drm/ci: add helper script update-xfails.py

Add helper script that given a gitlab pipeline url, analyse which are
the failures and flakes and update the xfails folder accordingly.

Example:
Trigger a pipeline in gitlab infrastructure, than re-try a few jobs more
than once (so we can have data if failures are consistent across jobs
with the same name or if they are flakes) and execute:

update-xfails.py https://gitlab.freedesktop.org/helen.fornazier/linux/-/pipelines/970661

git diff should show you that it updated files in xfails folder.

Signed-off-by: Helen Koike <helen.koike@collabora.com>
Tested-by: Vignesh Raman <vignesh.raman@collabora.com>
Reviewed-by: David Heidelberg <david.heidelberg@collabora.com>
Link: https://lore.kernel.org/r/20231024004525.169002-4-helen.koike@collabora.com
Signed-off-by: Maxime Ripard <mripard@kernel.org>