Show all runners for group (2)

What does this MR do and why?

Implements #337838 (closed), depends on backend at !96770 (merged)

This change adds a toggle that enables group owners to see more details of the available runner fleet by enabling them see "all" runners that are available.

Changelog: added

MR
Display shared runner details to group owners (1) (!99084 - merged)
Show all runners for group (2) (!97108 - merged)	☝ you are here!
Add feature tests and documentation to "show on... (!99087 - merged)

Screenshots or screen recordings

How to set up and validate locally

0. Enable runners_finder_all_available (rails c and then Feature.disable(:runners_finder_all_available))
1. With at least one shared/instance runner registered
2. Visit Admin -> Runners to register one http://gdk.test:3000/admin/runners
3. With at least one group and one runner in your group
4. My Group -> CI/CD -> Runners http://gdk.test:3000/groups/<group>/-/runners
5. Visit My Group -> CI/CD -> Runners
6. Click on "Show only my runners" to enable the full list.

Suggestion: Group Admin users see the same results, but with a different access level, as they may not edit/delete some runners:

Admin	Group Owner	sm screens

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #337838 (closed)