Revoking privileges from RBAC roles using v_generate_user_grant_revoke_ddl

When attempting to `DROP ROLE my_role` I received the error:

```
[55006] ERROR: role "my_role" cannot be dropped because the role has a privilege on some object
```

It would be great if we could use the [v_generate_user_grant_revoke_ddl.sql](https://github.com/awslabs/amazon-redshift-utils/blob/master/src/AdminViews/v_generate_user_grant_revoke_ddl.sql) script to generate the same content we can for users and groups, e.g:

```sql
SELECT ddl
FROM admin.v_generate_user_grant_revoke_ddl
WHERE ddltype = 'revoke'
AND (grantee = 'my_role' OR grantor = 'my_role')
ORDER BY objseq, grantseq DESC;
```

This might be similar to: https://github.com/awslabs/amazon-redshift-utils/issues/620

Without this do you know how we can find the privileges a role has?

Start by reading src/AdminViews/v_generate_user_grant_revoke_ddl.sql and compare its handling of users and groups with the requested RBAC role case. Use the provided query and the DROP ROLE failure as the reproduction; done means the view generates revoke DDL when the grantee or grantor is my_role.

Written by the indexing model from the issue text.