Resolve "Protected branches drop down does not show all users"
This MR refactors the implementation introduced in https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/581
Issues like #919 (closed) makes a refactor needed since the dropdowns were becoming too complex to maintain.
- Now the related dropdowns are based directly from
ProtectedBranchAccessDropdown
and its internal state is handled with JS only unlike its previous implementation that was a mix of JS and HTML inputs. - Now selected users are appended making them always visible.
Closes #919 (closed)