Moved the `get_token_from_default_dir` method to a common module for shared use between `gitlab_gql.py` and `ci_run_n_monitor.py`. This migration facilitates better code organization and potential future reuse. Signed-off-by: Guilherme Gallo <guilherme.gallo@collabora.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27206>