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>

models/repo.go

@@ -585,8 +585,7 @@ func (repo *Repository) getReviewers(e Engine, doerID, posterID int64) ([]*User,
 
 	var users []*User
 
-	if repo.IsPrivate ||
-		(repo.Owner.IsOrganization() && repo.Owner.Visibility == api.VisibleTypePrivate) {
+	if repo.IsPrivate || repo.Owner.Visibility == api.VisibleTypePrivate {
 		// This a private repository:
 		// Anyone who can read the repository is a requestable reviewer
 		if err := e.