Merge branch 'commits-api-better-trailers' into 'master'

Add an extended_trailers field to the commits API

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/136998



Merged-by: Michał Wielich <mwielich@gitlab.com>
Approved-by: Gavin Hinfey <ghinfey@gitlab.com>
Approved-by: Michał Wielich <mwielich@gitlab.com>
Reviewed-by: Michał Wielich <mwielich@gitlab.com>
Reviewed-by: Robert May <rmay@gitlab.com>
Co-authored-by: Robert May <rmay@gitlab.com>