trace_processor: Parse processDump

In addition to embedded systrace .html traces contain a "PROCESS DUMP"
section produced by [1] and (historically) parsed by [2]. This section
is the result of the command:
ps -A -o USER,PID,PPID,VSIZE,RSS,WCHAN,ADDR=PC,S,NAME,COMM && ps -AT -o USER,PID,TID,CMD
on the device.

This CL adds support in trace_processor for parsing these sections and
extracting process names and parent/child relationships.

[1]: https://github.com/catapult-project/catapult/blob/82f1741bbfa3a24eebace418c12cff5aca208ef2/systrace/systrace/tracing_agents/android_process_data_agent.py
[2]: https://github.com/catapult-project/catapult/blob/11513e359cd60e369bbbd1f4f2ef648c1bccabd0/tracing/tracing/extras/importer/android/process_data_importer.html

Bug: 143467493

Change-Id: I4dfd691b1730163e5b438e294a6f367bf231d239