Merge branch 'graphql_custom_fields_argument_for_issues_and_work_items' into 'master'

Graphql custom fields argument for issues

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/183391



Merged-by: Heinrich Lee Yu <heinrich@gitlab.com>
Approved-by: Heinrich Lee Yu <heinrich@gitlab.com>
Reviewed-by: Heinrich Lee Yu <heinrich@gitlab.com>
Co-authored-by: stefanosxan <sxanthopoulos@gitlab.com>