ScanRequestProxy: Send scan broadcasts for internal scan requests

ScanRequestProxy will listen to all "full" scan requests
handled by Wifiscanner and send out the broadcast & update
the internal cache. This will let 3p apps listen for results
from internal connectivity scan requests.

Also, removed the flag used in ScanRequestProxy to avoid sending
duplicate broadcasts for coalesced scans. This is no longer needed since
the global scan listener is guaranteed to be invoked just once for every
scan performed by the platform.

Bug: 119316884
Test: Unit tests
Test: CTS tests
Test: Verified scans from settings still works.
Test: Will send for regression tests.
Change-Id: I9353c9d8c82007eb08f19b2b799f8d4c694d9192
3 files changed