Cache permission policy

Since the Permission Controller calls into DPM, to avoid a potential
circular dependency (where the DPMS holds a lock while the Permission
Controller calls it), cache the permission policy.

Bug: 158735247
Test: atest com.android.cts.devicepolicy.MixedProfileOwnerTest#testDelegation com.android.cts.devicepolicy.MixedDeviceOwnerTest#testDelegation com.android.cts.devicepolicy.MixedManagedProfileOwnerTest#testDelegation
Test: atest com.android.cts.devicepolicy.MixedProfileOwnerTest#testPermissionAppUpdate com.android.cts.devicepolicy.MixedProfileOwnerTest#testPermissionPolicy com.android.cts.devicepolicy.MixedDeviceOwnerTest#testPermissionAppUpdate com.android.cts.devicepolicy.MixedDeviceOwnerTest#testPermissionPolicy com.android.cts.devicepolicy.MixedManagedProfileOwnerTest#testPermissionAppUpdate com.android.cts.devicepolicy.MixedManagedProfileOwnerTest#testPermissionPolicy
Change-Id: I6cfc027b063f43053d1ff4cc42d37935491064ff