ci: Namespace trace artifacts to the job number

ci: Namespace trace artifacts to the job number

Put artifacts in a per-job folder, because if a job is retried then it
will try to upload a file to the same key and fail with the following
error:

403 Client Error: Forbidden for url:
https://minio-packet.freedesktop.org/artifacts/daenzer/mesa/180609/gl-panfrost-t860/results.yml

Also, to prevent in the future similar clashes if several trace files
share the same name, upload the images with their checksums as their
names. This will also make it easier to fetch images for comparison with
the references.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Andres Gomez <agomez@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6029>