Support reverting a migration on a specific database

[grennis]

Is your feature request related to a problem? Please describe.
If I run migrate --revert, Fluent attempts to revert migrations on all attached databases. This is often not desired when migrations have been run independently on different databases over time.

Describe the solution you'd like
Add an optional db parameter, like migrate --revert --db psql

Describe alternatives you've considered
Maybe Fluent can check timestamps and only revert changes that were made together across databases, but this seems error prone.

Another option would be to query [Y/N] for the migration on each database instead of one [Y/N] prompt for all.

So currently I think the only way to support this is for the app developer to write a custom command.

Additional context
N/A