Switch proc stats to use new process state constants.

These new constants are a better mapping to the kind of
information that procstats is wanting to collect about
processes.  In doing this, the process states are tweaked
to have a bit more information that we care about for
procstats.

This changes the format of the data printed by procstats,
so the checkin version is bumped to 2.  The structure is
the same, however the codes for process states have all
changed.  The new codes are, in order of precedence:

p -- persistent system process.
t -- top activity; actually any visible activity.
f -- important foreground process (ime, wallpaper, etc).
b -- important background process
u -- performing backup operation.
w -- heavy-weight process (currently not used).
s -- background process running a service.
r -- process running a receiver.
h -- process hosting home/launcher app when not on top.
l -- process hosting the last app the user was in.
a -- cached process hosting a previous activity.
c -- cached process hosting a client activity.
e -- cached process that is empty.

In addition, we are now collecting uss along with pss
data for each process, so the pss checkin entries now
have three new values at the end of the min/avg/max uss
values of that process.

With this switch to using process state constants more
fundamentally, I realized that they could actually be
used by the core oom adj code to make it a lot cleaner.
So that change has been made, that code has changed quite
radically, and lost a lot of its secondary states and flags
that it used to use in its computation, now relying on
primarily the oom_adj and proc state values for the process.

This also cleaned up a few problems -- for example for
purposes of determing the memory level of the device, if a
long-running service dropped into the cached oom_adj level,
it would start being counted as a cached process and thus
make us think that the memory state is better than it is.
Now we do this based on the proc state, which always stays
as a service regardless of what is happening like this, giving
as a more consistent view of the memory state of the device.

Making proc state a more fundamentally part of the oom adj
computation means that the values can also be more carefully
tuned in semantic meaning so the value assigned to a process
doesn't tend to change unless the semantics of the process
has really significantly changed.

For example, a process will be assigned the service state
regardless of whether that services is executing operations
in the foreground, running normally, or has been dropped to
the lru list for pruning.  The top state is used for everything
related to activities visible to the user: when actually on
top, visible but not on top, currently pausing, etc.

There is a new Context.BIND_SHOWING_UI added for when system
services bind to apps, to explicitly indicate that the app
is showing UI for the system.  This gives us a better metric
to determine when it is showing UI, and thus when it needs
to do a memory trim when it is no longer in that state.  Without
this, services could get in bad states of continually trimming.

Finally, more HashSet containers have been changed to ArraySet,
reducing the temporary iterators created for iterating over
them.

Change-Id: I1724113f42abe7862e8aecb6faae5a7620245e89