Add Visible modes function from Organisation to Users too (#16069)

You can limit or hide organisations. This pull make it also posible for users

- new strings to translte
- add checkbox to user profile form
- add checkbox to admin user.edit form
- filter explore page user search
- filter api admin and public user searches
- allow admins view "hidden" users
- add app option DEFAULT_USER_VISIBILITY
- rewrite many files to use Visibility field
- check for teams intersection
- fix context output
- right fake 404 if not visible

Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: Andrew Thornton <art27@cantab.net>

docs/content/doc/advanced/config-cheat-sheet.en-us.md

@@ -512,6 +512,7 @@ relation to port exhaustion.
 - `SHOW_MILESTONES_DASHBOARD_PAGE`: **true** Enable this to show the milestones dashboard page - a view of all the user's milestones
 - `AUTO_WATCH_NEW_REPOS`: **true**: Enable this to let all organisation users watch new repos when they are created
 - `AUTO_WATCH_ON_CHANGES`: **false**: Enable this to make users watch a repository after their first commit to it
+- `DEFAULT_USER_VISIBILITY`: **public**: Set default visibility mode for users, either "public", "limited" or "private".
 - `DEFAULT_ORG_VISIBILITY`: **public**: Set default visibility mode for organisations, either "public", "limited" or "private".
 - `DEFAULT_ORG_MEMBER_VISIBLE`: **false** True will make the membership of the users visible when added to the organisation.
 - `ALLOW_ONLY_INTERNAL_REGISTRATION`: **false** Set to true to force registration only via gitea.