scripts/ci: update gitlab-runner playbook to use latest runner

scripts/ci: update gitlab-runner playbook to use latest runner

We were using quite and old runner on our machines and running into
issues with stalling jobs. Gitlab in the meantime now reliably provide
the latest packaged versions of the runner under a stable URL. This
update:

  - creates a per-arch subdir for builds
  - switches from binary tarballs to deb packages
  - re-uses the same binary for the secondary runner
  - updates distro check for second to 22.04

Note this script isn't fully idempotent as we end up accumulating
runners especially during testing. However we also want to be able to
run twice with different GitLab keys (e.g. project and personal) so I
think we just have to be mindful of that during testing.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Acked-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230124180127.1881110-2-alex.bennee@linaro.org>