Add Snowflake Integrations

Merge Request Checklist

• Link to an issue
• Include the proposed fix or feature
• Include and update tests for the modified code
• Include a documentation change
• Add an entry in the Unreleased section of the CHANGELOG

Addition of Snowflake Integrations. The integration object in Permifrost will be similar to Warehouses. Indeed Integrations are living on a snowflake account not on a particular schema or database, their behavior (in terms of permissions) is quite similar to warehouses but only for usage. I adapted warehouses functions to work with integrations in this MR.

It is part of issue #121 but does not close it in full.

Once your merge request is complete, please assign it the Permifrost maintainers using the /assign_reviewer @gitlab-data/permifrost_maintainers placed in a comment for the review cycle. Once the review cycle is finished, the reviewer shall approve the merge request so it can be merged by any Permifrost developer, maintainer, or owner.