Add Group milestones API (GET) methods to api.js

Problem to solve

As a breakdown of #121476 (comment 384809928), one thing we'll want to do is add methods to api.js to get Group milestones. We'll want this so that we can populate the milestones dropdown combobox with Group milestones to select from to be associated (or unassociated) with a release.

For the purpose of this problem, we likely only need methods for these two API calls:

GET /groups/:id/milestones
GET /groups/:id/milestones?search=version

Intended users

User experience goal

As an internal developer, it should be possible to get and search for group milestones using tested methods in api.js.

Proposal

Add methods to api.js to get Group milestones using these endpoints:

GET /groups/:id/milestones
GET /groups/:id/milestones?search=version

Further details

This benefits the development of #121476 (comment 384809928) by making it possible to populate the proposed milestone dropdown combobox.

Permissions and Security

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  • Add expected impact to Reporter (20) members
  • Add expected impact to Developer (30) members
  • Add expected impact to Maintainer (40) members
  • Add expected impact to Owner (50) members

Availability & Testing

Unit tests should be added to api_spec.js