Add prompt for users removing themselves from groups and subgroups

Problem

As per this ticket: https://gitlab.zendesk.com/agent/tickets/286151

User is requesting to have the ability to remove themselves from groups/subgroups.

Removing direct membership on parent groups should also remove any explicit direct membership of child groups without making any changes to SAML while remaining an Owner of all subgroups via inherited permissions.

Users have owner permissions throughout, it's just direct membership that is being removed.

Proposal

Users should have the ability to be prompted if they want to be removed from groups/subgroups.

The default action for both the UI and API should be to remove only the direct membership of the group being actioned. Any direct child group memberships would be left in place.

We could use a similar interaction as shown when removing a member: