Expose webhook name and description fields in API

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/152497



Merged-by: Luke Duncalfe <lduncalfe@gitlab.com>
Approved-by: Ashraf Khamis <akhamis@gitlab.com>
Approved-by: Ivane Gkomarteli <igkomarteli@gitlab.com>
Approved-by: Luke Duncalfe <lduncalfe@gitlab.com>
Co-authored-by: bmarjanovic <bmarjanovic@gitlab.com>