[Feat.Req] Garbage collect finished SenderAllocationRelationships

[aasseman]

Problem statement
TAP Agent will currently tell SenderAllocationRelationships to do their last RAV request when an allocation or a sender become ineligible. The actual RAV request is done asynchronously and therefore the finished SenderAllocationRelationships cannot be removed immediately.

Expectation proposal
There needs to be a process that will check SenderAllocationRelationships that are finished and deletes them. Ideally in a separately spawned async task of some sort.

Additional context

indexer-rs/tap-agent/src/tap/sender_allocation_relationships_manager.rs

Lines 288 to 289 in 1178c63

	// TODO: remove SenderAllocationRelationship instances that are finished. Ideally done in
	// another async task?

[aasseman]

Made obsolete by #137