Remove Mathesar schemas when databases are disconnected

[pavish]

Description

• In our current master, we provide the user with a checkbox to remove Mathesar schemas (msar, __msar, and mathesar_types) when they are deleting a database connection.
• With our new setup, we do not have a clear way of doing this yet since we may or may not have the password of the owner role of the Mathesar schemas configured (i.e. it may be deleted by the user after configuration).
• We need to figure out how to allow removing Mathesar schemas when disconnecting a database.