Implement roles.delete, databases.drop & databases.configured.disconnect endpoints

[Anish9901]

Fixes #3772
Fixes #3841
Fixes #3842

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[pavish]

Looks good. I have a couple comments that require discussions, but no changes needed in this PR.

[pavish]

I've been thinking more about this and we should only be providing 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:

1. The user should be a Mathesar admin
2. The database should be present within the internal db server
3. 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
• disconnect
• connect to the internal db server with the internal db role
• drop the database

[pavish]

Nothing needed in this PR, we can do this for beta.

[pavish]

We need to discuss on how to remove the Mathesar schemas. This requires a broader discussion on how we'll retain/request the user for the role & password for the role that owns the schemas.

We can get back to this before beta.