- all commits squashed to make danger review happy

Includes changes to the Vue container registry component to support
the display of an empty message and error message when invalid
characters are found in the group, project or branch name.

repositories/index.html.haml has been changed to remove the content
and place into Vue component.

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

A recent update in [GitLab UI] and setting the [config.assets.paths] to
include `node_modules` for the resolution of SCSS imports, allows us to
have much nicer imports which don't rely on brittle relative paths.

This change also forwards @gitlab/ui to the newest version

[GitLab UI]: https://gitlab.com/gitlab-org/gitlab-ui/merge_requests/602
[config.assets.paths]: https://gitlab.com/gitlab-org/gitlab-ce/blob/d9026d0ffa0/config/application.rb#L169

- next-discuss button is always show unless there is only 1 discussion
- regroup buttons arrangements

Updated the toast action selector to `first-of-type` instead

Use darker gray color for system note metadata and edited text

Closes #62938

See merge request gitlab-org/gitlab-ce!30054

On all the issue lists -- Group, Project and Dashboard -- this
change adds a new option for managing the lists.

"Manual Ordering" option is added which when flipped on will allow
an user to drag and drop issues around to create a relative ordering
among them.