This CL includes the new Java API that supports async network scans.
Applications could get faster network scan results with this new API.
The long-term goal is to support Subsecond Switching which is separate
from what this CL is doing.
Bug: 30954762
Test: Unit test, run runtest -x NetworkScanRequestTest.java
Change-Id: I78cadaf838dee8439fe7417ef39f689990bf5705
(cherry picked from commit fdfb6f4d2f)
