ScannerImpl: Add unit tests for scheduled scans

This patch adds unit tests for scheduled scans.
In order to do that, this also moves the isOffloadScanSupprted()
out of OffloadScanManager to OffloadServiceUtils. By injecting
MockOffloadServiceUtils to ScannerImpl, we can test either offload
supported or not supported cases.

Bug: 33452931
Test: compile, unit tests
Test: manual test that offload scan is not enabled by mistake.
This is done by checking manually inserted logs.

Change-Id: I6c78df78605321013676e5f4578026f21d953e3b
12 files changed