[CT-716] Snowflake: Add Grants to Materializations

[nathaniel-may]

blocked by: dbt-labs/dbt-core#5263

Once the above work is merged into core, there are some tweaks that need to be made in the Snowflake adapter to fully expose the feature:
- [ ] add a call to apply_grants(..., revoke=True) to all custom materializations
- [ ] in view/table materializations, call apply_grants(..., revoke=False) instead for a performance improvement

• Add a test for the interaction with copy_grants

[jtcohen6]

• get_grant_sql: https://docs.snowflake.com/en/sql-reference/sql/grant-privilege.html (I think the default should work)
• get_revoke_sql: https://docs.snowflake.com/en/sql-reference/sql/revoke-privilege.html (I think the default should work)
• get_show_grants_sql: https://docs.snowflake.com/en/sql-reference/sql/show-grants.html (different from PostgreSQL — but we might want to make this the default?)