Work on issue #38242094: Activity manager oom adj computation seems broken

This shouldn't change any behavior, but improve the reason we
report for each process's oom_adj / proc state level.  There are
two significant things going on here:

1. We now consider a bump up in proc state to be just as significant
as a change in oom_adj, and accordingly update the reason when this
happens.  Given how many proc stats we now have mapped to some of
the single oom_adj levels, this matches your expectation to have the
reason be why it is at that proc state and not just some random
other thing at that level.

2. There is special handling of an app at the top state connecting
to another app, deciding the actual state to apply at the end.  This
was not at that point updating the reason, so anything the top app
is connected to would get the top state but myseriously have some other
reason, looking very broken.  We now propagate the reason over.

Test: manual

Change-Id: Idecbe206d73e7c4cbd989ef6faf3b1679e06c088