Optimize stack trace reporting puller for speed.

Resampling new package takes some time (because of PackageManager
related queries), while it is not necessary to perform it immediately
after stack trace was collected. To minimize puller running time
we offloaded resampling task to background thread.

Test: statsd_testdrive 10069 && atest RuntimeMessageCollectionTest
Bug: 143519689
Change-Id: Iac4637ca5ad81ccb20792b7d3faccd652571dc40