Implement #10749688: Improve low memory reporting

This significantly reworks the logging we do when
all cached processes are killed:

- We now collect the list of processes in-place so we
  have a snapshot of exactly when the low memory situation
  happened.
- In that snapshot we include the key process state: oom
  adj, proc state, adj reasons.
- The report then asynchronously collects pss information
  for those processes.
- The ultimate data printed to the log looks like a mix
  between the "dumpsys meminfo" and "dumpsys activity"
  output.  This code no longer uses "dumpsys meminfo"
  itself, so some of that data is no longer included,
  in particular pss organized by allocation type.

In doing this, I realized that the existing code that is
supposed to run "procstats" is not currently working.  And
at that point I realized, really, when we are collecting
this pss data we'd really like to include all those native
processes using ghod-only-knows how much RAM.  And guess
what, we have a list of processes available in
ProcessCpuTracker.

So we now also collect and print information for native
processes, and we also do this for "dumpsys meminfo" which
really seems like a good thing when we are printing summaries
of all pss and such.

I also improved the code for reading /proc/meminfo to be
able to load all the interesting fields from there, and
am now printing that as well.

Change-Id: I9e7d13e9c07a8249c7a7e12e5433973b2c0fdc11