subscriptions: group leader can remove group members

Allow group leads to remove members from the subscription tab (#1662)

* checkpoint commit

* First attempt at working code

* Move hook outside function definition

* Hopefully fix trash icon

* Try to fix hook call

* Try to improve trash icon look

* Fix import

* Add basic tooltip and user confirmation dialog

* Expire group member list if user leaves a group

* Don't show trashcan for this user

* Fix verbiage

* Factor shared string to a constant

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Co-authored-by: Ryan Doherty <rdoherty@cedar.penn.apidb.org>
(cherry picked from commit 2eae8a72e76f83021183c0a1ad59d8459c011bb0)