Edit Branch Rules: Update selector to support searching Deploy Keys

Context

Scenario the selector for Deploy keys used in:

"Allowed to push and merge" screen

Allows editing of roles, users, groups, and deploy keys
Default: (empty)
Empty state text: Everyone is required to submit a merge request for changes.
On change, display toast "Allowed to push and merge updated"
- Undo action would be nice to have.

Default	Edit - filled	Allowed to push and merge updated

Proposal

Update the reusable frontend component built in #428519 (closed) and make it support searching and selecting deploy keys.

This will be used in these contexts:

Branch Protections
- Allowed to push and merge

Details

We have two more cases for a extremely similar component:

Users
Groups

They seem to share the UI and IxD, only changing the objects being searched.

This should be taken into consideration when extending this foundational component to allow for easy customization of the queries and wording on the UI.

Mockup

See mockups in the epic and figma: