Draft: ci/lava: Add graceful exit on signal handling

What does this MR do and why?

The update introduces signal handling functionality in the LAVA job
submission process, allowing the system to gracefully exit upon
receiving signals such as SIGTERM, SIGINT, or SIGQUIT. This enhancement
is in response to GitLab now sending SIGTERM to jobs before canceling
them, enabling better management of LAVA tasks.

TLDR: Actually cancel the LAVA job when Gitlab job is cancelled.

See also: https://gitlab.com/gitlab-org/gitlab-runner/-/issues/6359