Some time ago populating of tables from sstables was reworked to use sstable states instead of full paths (#12707). Since then few places in the populator was left that still operate on the state-based subdirectory name. This PR collects most of those dangling ends
refs: #13020Closesscylladb/scylladb#15421
* github.com:scylladb/scylladb:
distributed_loader: Print sstable state explicitly
distributed_loader: Move check for the missing dir upper
distributed_loader: Use state as _sstable_directories key