A typed map sharing one column family with other typed maps,
distinguished by a tag byte prefixed to every key: the big-endian fixint
serialization of (tag, key) keeps each map a contiguous key range of
the column family. Useful for sets of tables that are always created and
dropped together — one column family instead of one per table keeps the
column-family and SST-file counts low.
Waits until the database of db has been closed, every handle to it
dropped and RocksDB’s files released, so its directory can be reopened,
moved, or deleted. Returns false if it is still open after 30 seconds.