Prune logic from buffer stuffing recovery using UIDs

Buffer stuffing recovery was initially implemented using
UIDs and sending events to subscribed clients. A different,
simpler approach using callbacks when blocked on dequeueBuffer
has since been favored (change-id I24e34591e809aebd7626657c6340faed323227ad)
and leaves the initial UID event subscription logic obsolete.

Leaving this code causes issues since the logic attempts to
update an event that is part of union, causing issues in other
events that do not hold onto the current object.

This is a partial revert of change-id I38f0eb3d6ef1331e07d6022fa3a0e16c556ba06f

Bug: b/294922229
Test: presubmit
Flag: EXEMPT, code cleanup
Change-Id: I53f653550c58376c8d82a491ecf0aebdeeafbc0d