In #23977 we moved the keyring into Raft, which can expose key material in Raft
snapshots when using the less-secure AEAD keyring instead of KMS. This changeset
adds tools for redacting this material from snapshots:
* The `operator snapshot state` command gains the ability to display key
metadata (only), which respects the `-filter` option.
* The `operator snapshot save` command gains a `-redact` option that removes key
material from the snapshot after it's downloaded.
* A new `operator snapshot redact` command allows removing key material from an
existing snapshot.
The `operator snapshot` commands and agent don't back up Nomad's key
material. Add some warnings about this to places where users might be looking
for information on cluster recovery.
Fixes: https://github.com/hashicorp/nomad/issues/19389
When cluster administrators restore from Raft snapshot, they also need to ensure the
keyring is in place. For on-prem users doing in-place upgrades this is less of a
concern but for typical cloud workflows where the whole host is replaced, it's
an important warning (at least until #14852 has been implemented).
The sidebar navigation tree for the `operator` sub-sub commands is
getting cluttered and we have a new set of commands coming to support
secure variables keyring as well. Move these all under their own
subtrees.
