Show database names in spacetime list

[clockwork-labs-bot]

Summary

• add a db_names column to spacetime list
• keep the database identity column too
• use reverse-DNS lookups to show all known names for each database
• degrade gracefully if a reverse lookup fails instead of failing the whole command

Closes #1046.

Notes

I looked at #1072 for prior art. This version is adapted to the current spacetime list implementation and uses the existing util::spacetime_reverse_dns helper rather than calling the endpoint directly.

If a database has no names, the command prints (unnamed).
If a reverse-DNS lookup fails, the command prints (lookup failed) for that row and warns on stderr.

Testing

• cargo check -p spacetimedb-cli

[bfops]

LGTM