This leaves only the existence of isolated_app domain as public API.
All other rules are implementation details of this domain's policy and
are thus now private.

Test: No change to policy according to sesearch, except for
      disappearance of all allow rules from isolated_app_current
      attribute (as expected).
Bug: 31364497

Change-Id: I499a648e515628932b7bcd188ecbfbe4a247f2f3