Allow a Release's associated Milestones to be edited through the "Edit Release" page
Problem to solve
Changing a Release's associated Milestones is only possible through the Releases API.
Add a new field to the "Edit Release" page that allows a user to add/remove/change the Milestones associated to the Release.
Releases can be associated with 0, 1, or multiple Milestones.
This feature should also be available when creating a new Release through the UI (not yet implemented - see #39464 (closed)).
This page will likely need to be updated with new screenshots and instructions.