Change/remove a branch of an open issue (#9080)

* Add field with isIssueWriter to front end

* Make branch field editable

* Switch frontend to form and POST from javascript

* Add /issue/id/ref endpoint to routes

* Use UpdateIssueTitle model to change ref in backend

* Removed crossreference check and adding comments on branch change

* Use ref returned from POST to update the field

* Prevent calling loadRepo from models/

* Branch/tag refreshed without page reload

* Remove filter for empty branch name

* Add clear option to tag list as well

* Delete button translation and coloring

* Fix for not showing selected branch name in new issue

* Check that branch is not being changed on a PR

* Change logic

* Notification when changing issue ref

* Fix for renamed permission parameter

* Fix for failing build

* Apply suggestions from code review

Co-authored-by: zeripath <art27@cantab.net>

Co-authored-by: Gitea <gitea@fake.local>
Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

options/locale/locale_en-US.ini

@@ -760,6 +760,7 @@ code = Code
 code.desc = Access source code, files, commits and branches.
 branch = Branch
 tree = Tree
+clear_ref = `Clear current reference`
 filter_branch_and_tag = Filter branch or tag
 branches = Branches
 tags = Tags