Add more information to incident header. Especially add config keys

to check if the report is uploadable.

Move incidentheader.proto to libincident so statds is able to include a lite
proto class for incident header.

Change IncidentReportArgs to add the proto object instead of serialized
bytes to prevent caller gives meaningless data.

Bug: 70241842
Test: push config to statsd and verify incidentd generate the report
with correct header.

Change-Id: If95b655be71047b019b229e5903a08f3c21a1f29