After scylladb/scylladb#22034, staging status of sstables streamed
via file streaming was ignored and view updates were never generated.
This patch fixes it and now staging sstables are registered to
`view_building_worker`. Then, the worker create view building tasks
for those sstables, so the view building coordinator can schedule them
once the tablet migration is finished.
Fixesscylladb/scylla-enterprise#4572