Statsd -> Perfetto integration

This CL invokes the perfetto client utility to start the
collection of a trace when an anomaly that subscribed to
Perfetto is detected. The code simply spawns the
/system/bin/perfetto client and passes the trace config via
stdin. The client takes care of the dropbox upload.
The CollectPerfettoTraceAndUploadToDropbox() function does
NOT wait for the full trace collection (in order to avoid
blocking statsd) and instead returns immediately after having
spawned perfetto.

Change-Id: I4f02067bad7a46ede7b6e4841cdcf381c1a4e2a7
Bug: 71795552