clickhouse-admin-client is missing API metadata

[davepacheco]

If you run cargo xtask ls-apis apis (or any other subcommand), you get this warning:

$ cargo xtask ls-apis apis
...
warning: workspace omicron: found client package missing from API manifest: clickhouse-admin-client
...

This is because we've recently added a package called clickhouse-admin-client that depends on Progenitor. ls-apis correctly infers that it's a Progenitor-based API client. But it has no metadata about the API.

[andrewjstone]

I can likely take care of this when working on #6779

[davepacheco]

I wound up doing it in #6830, for what it's worth.