Extend approvers_select component to group level

What does this MR do and why?

Extend approvers_select component to group level. Currently it is only supported on the project level.

Depends on theses backend changes: !95195 (merged)

Related issue: #369492 (closed)

Screenshots or screen recordings (No changes in the UI)

Project settings -> general -> merge request approvals

Security & Compliance -> Policies -> Scan result policy

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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