Reroute surfaceflinger atoms through system server

System server changes for routing surfaceflinger pulled atoms through
system server. Pullers are registered in StatsPullAtomService. All logic
is done in JNI since SurfaceComposerClient is only available in native.
The JNI structure is modeled off of ag/10209693.

Test: statsd_testdrive 10062 10063
Bug: 184698814
Change-Id: I55c75c485f49f75367cc285a84f12f316139241b