Implement dropping databases

[pavish]

Description

• We have Implement roles.delete, databases.drop & databases.configured.disconnect endpoints #3858 which implements dropping databases, but it requires us to connect to another database in the same server with the same role which is the owner of the database-to-be-dropped. This is not always feasible and currently not possible with our UX. This issue details some recommendations:

We should probably only provide delete for databases created in the internal server. Only Mathesar admins should be able to perform this.

When the user requests a delete, these conditions should match:

• The user should be a Mathesar admin
• The database should be present within the internal db server
• The collaborator must use a role that owns the database

And then, in a single transaction:

• Connect to the database that's about to be deleted
• Change ownership to the internal db role that we use in mathesar_django
• Connect to the internal db server with the internal db role
• Drop the database