odrefresh: check artifacts using cache and filesystem metadata

Renables checking of artifacts when invoked with "--check".

Replaces the former "--check" code with a lightweight method based on
artifact cache metadata and filesystem metadata. The worst case checks
take 60ms on aosp_blueline-userdebug.

The old "--check code" is now invoked with "--verify". This remains
for testing purposes and as an option for post-compilation checking.

Bug: 160683548
Bug: 181689036
Test: manual module installs, reboots, deleting artifacts.

Change-Id: I2a75e0fde032a8e3a29d105d8b52e1ede6cb764d
7 files changed