Update imgdiag scripts

run_imgdiag:
* Add PID to output filenames.
* Add option to specify host output directory.

create_dirty_image_objects:
* Add an option to merge imgdiag files with the same process names.
* Improve object sorting.
* Print stats in csv format.

Test: ./run_imgdiag.py --host-out-dir out
Test: ./create_dirty_image_objects.py ./out/imgdiag_* --merge-same-procnames --print-stats
Change-Id: I94aba7b241e0a0c2ebfb33ffcc333640c04f2d01