All issue boards can now be collapsed via a button, re-ordered by
dragging the header, and the vertical collapsed header style was
reworked.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/59895

This reverts merge request !27313

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/59895

* dropdown position
* add empty state list overflow
* avoid double scrollbars in project dropdown

Signed-off-by: Tao Wang <twang2218@gmail.com>

Adjusts regression fixed by https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/18786/. We were not returning the label text color correctly on the backend.

Added by
https://gitlab.com/gitlab-org/gitlab-ee/commit/88aea2cbc8633ba970335d935d725bd17654b424

Part of this MR: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1797/

[ci skip]

The closed & backlog lists in issue boards are no collapsible. They can
be collapsed independently of each other & this selection is then saved
to the browser through localStorage. When the page loads, the code gets
the data from localStorage & determines whether to show or hide the list

Closes #23917

Aim to eventually go to vue files