Unable to remove databases which can't be connected to

[zackkrida]

Description

If a user has deleted or otherwise lost access to one of their Postgres databases, it follows that they would want to remove the database from Mathesar.

Currently, it doesn't seem that Mathesar can remove databases which cannot be connected to:

Expected behavior

Remove the DB from Mathesar but inform the user that Mathesar is unable to connect to the DB. Perhaps, if the user wishes to drop the DB and/or remove Mathesar's schema, we should not delete the Database from Mathesar. Rather, we should inform the user "The selected actions can't be completed because Mathesar is unable to connect to your database. Either repair the connection or uncheck 'Drop the database' or 'Remove Mathesars internal schema' features to continue removing the database from Mathesar"

To Reproduce

1. Create a DB somewhere, add it to Mathesar.
2. Delete or revoke access to the DB.
3. Try to remove it in the Mathesar UI.