Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Closes #21071

This helper adds a datepicker to all `js-access-expiration-date`
elements. If that element is a child of a `clearable-input` element and
has a sibling `js-clear-input` element, then it will show a working
clear button to the right of the input field.

Also updates protect branch list

1. Instantiate `ProtectedBranchesAccessSelect` from `dispatcher`

2. Use `can?(user, ...)` instead of `user.can?(...)`

3. Add `DOWNTIME` notes to all migrations added in !5081.

4. Add an explicit `down` method for migrations removing the
   `developers_can_push` and `developers_can_merge` columns, ensuring that
   the columns created (on rollback) have the appropriate defaults.

5. Remove duplicate CHANGELOG entries.

6. Blank lines after guard clauses.