The Kafka Metadata shell is a new command which allows users to
interactively examine the metadata stored in a KIP-500 cluster.
It can examine snapshot files that are specified via --snapshot.
The metadata tool works by replaying the log and storing the state into
in-memory nodes. These nodes are presented in a fashion similar to
filesystem directories.
Reviewers: Jason Gustafson <jason@confluent.io>, David Arthur <mumrah@gmail.com>, Igor Soarez <soarez@apple.com>