Merge branch 'epic-dropdown' into 'master'

Convert epic dropdown to GlDisclosureDropdown

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/127410



Merged-by: Olena Horal-Koretska <ohoralkoretska@gitlab.com>
Approved-by: Sascha Eggenberger <seggenberger@gitlab.com>
Approved-by: Olena Horal-Koretska <ohoralkoretska@gitlab.com>
Reviewed-by: Annabel Dunstone Gray <annabel.dunstone@gmail.com>
Reviewed-by: Olena Horal-Koretska <ohoralkoretska@gitlab.com>
Reviewed-by: Peter Hegman <phegman@gitlab.com>
Co-authored-by: Annabel Dunstone Gray <annabel.dunstone@gmail.com>