Theoretically safer due to avoiding a potential data race (change in
`leasedInProgress` between the time of the check and start of schedule
execution).
Improves reliability by being fail-safe in case of multiple returns,
which can happen if the operation tracker is part of a screen being
exited (as is the case with its current primary usage in multiplayer).
Finishing an operation started via
`OngoingOperationTracker.BeginOperation()` was risky in cases where the
operation ended at a callback on another thread (which, in the case of
multiplayer, is *most* cases). In particular, if any consumer registered
a callback that mutates transforms when the operation ends, it would
result in crashes after the framework-side safety checks.
Rework `OngoingOperationTracker` into an always-present component
residing in the drawable hierarchy, and ensure that the
`operationInProgress` bindable is always updated on the update thread.
This way consumers don't have to add local schedules in multiple places.
