Benchmarks to measure CursorWindow overheads.

We have some ideas on how to improve the efficiency of CursorWindow
transport for smaller data sets, but we want to get some benchmarking
in place to better characterize our upcoming changes.

These tests move a small, medium, and large cursor across process
boundaries, exercising the typical ContentProvider.query() flow.

Bug: 169251528
Test: ./frameworks/base/libs/hwui/tests/scripts/prep_generic.sh little && atest CorePerfTests:android.database.CrossProcessCursorPerfTest
Change-Id: Ia9e6a3195324db93a02d224e8b5108d397e3bb41