Allow the system to specify user-force when restricting.

There are certain situations where user-force is the right reason to
apply when placing an app in the RESTRICTED bucket, but the previous
APIs didn't allow for those situations. Introduce a new one to account
for those scenarios.

Bug: 183103253
Test: atest AppStandbyControllerTests
Change-Id: Ifbdc7de8975f31110224b7c20328f9c53abe68d9