service: Add LE scan support to Binder API

Added Binder API documentation, bindings, and logic for BLE device
scans. Also added the start-le-scan and stop-le-scan commands to
bluetooth-cli for testing.

Bug: 25744656
Change-Id: I08c9d23ddd78cff1702495cf6d431cf5b9a7b894
5 files changed