FE: Handle role change switch for Promotion Approval

When a member's role is changed through the members table UI dropdown, and that change requires Promotion Approval — we should restore the UI dropdown to a previous state.

Adding a recording of current behaviour in MR implementing promotion approval queue by @suraj_tripathy: queuing.mov

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As a stretch goal (might have separate issue) we should display a post-change notification that instead of role change, a request was created.

As a stretch goal (might have separate issue) we should update the page, or update the table, or refetch the pending approval members, to also include this new request.

Follow-up from #433172 (closed)