Move heavy-weight process state down to cached range.

This allows us to generally treat heavy-weight processes in
the background as cached processes, applying all of the limitations
we want for such things -- disable wake locks, etc.

Test: run-am-test ActivityManagerProcessStateTest
Bug: 63937884
Change-Id: I7c140c8f48188f6aa9c09731e83e3db4e4405e77