Add support for Global Privileges

Describe the feature

As of now, Permifrost supports Database, Schema and Table privileges. Snowflake has all kinds of privileges levels, "Global Privileges" between them. Adding support for that would be super helpful.

Describe alternatives you've considered

For now we're just running queries to grant these privileges manually.

Additional context

Who will this benefit?

This will be helpful for all kinds of things, especially for Snowflake account admins because they will be able to delegate some of these tasks to other roles through Permifrost

Are you interested in contributing this feature?

I'd love to contribute some code in here.