gitlab-ci: add python script to submit lava jobs

gitlab-ci: add python script to submit lava jobs

Covert the job submission process to a python script for more
robustness and control. allowing easier manipulation of job data.

As a result, it adds retry logic to deal with Infrastructure Errors in LAVA.

_call_proxy() is equipped with a robust retry logic, which I have been
using already in the past few weeks in stress testing to run hundreds
of jobs.

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11079>