Snowflake CoWork Automations: EXECUTE AGENT TASK privilege granted to PUBLIC by default

Snowflake CoWork Automations access behaves as follows:

New privilege:

The EXECUTE AGENT TASK privilege on the account is granted to the PUBLIC role by default. Administrators can still revoke the privilege from PUBLIC and grant it only to selected roles.

This additive change reduces onboarding friction for Snowflake CoWork Automations while preserving administrator control to restrict access when needed.

Ref: 2349