doc: move policy docs to the permissions scope

During the journey of the Permission System, we've felt the necessity to expand the policy documentation to include the permissions (#44004). The principal idea is to avoid confusion between policy and permissions.

Note: I've included the Process-based permission just to simulate how it gonna work along with the Permission System. Once it's approved, I'll remove and keep just the Resource-based permission.

Reference: https://github.com/nodejs/security-wg/issues/791#issuecomment-1212681390