Merge branch '371931-content-editor-on-issues' into 'master'

[Feature flag] Allow using the Content Editor to edit issuable descriptions

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/98703



Merged-by: Simon Knox <simon@gitlab.com>
Approved-by: Niko Belokolodov <nbelokolodov@gitlab.com>
Approved-by: Rahul Chanila <rchanila@gitlab.com>
Approved-by: Simon Knox <simon@gitlab.com>
Co-authored-by: Enrique Alcantara <ealcantara@gitlab.com>