Snapshot memory state for some native processes

Which processes to snapshot is controlled by a whitelist.

Benchmark for taking the snapshot:
https://docs.google.com/spreadsheets/d/1vG9ku8Uu8104CmKbO4cNeEKVeeByvHY--p0_dK1GAdA/edit?usp=sharing
(The difference between the first two sheets.)
~20ms constant cost plus ~4ms per process.

Bug: 115968899
Test: manually verified that statsd is included in the report
Change-Id: Iba680531c563ba28fae849e44044313866b2103f