WindowManagerUtil for hostside tests

Create a new hostside common utils module, and
add a WindowManagerUtil that processes WindowManagerService proto dumps.

A recent change in how WindowManagerService dumps its information
required changes in multiple tests, and it is more cumbersome
to iterate over all windows now, so extract that logic to a common
utility class.

The shared hostside util library "compatibility-host-util" lives in
platform/test/suite_harness which is developed in AOSP, so cannot keep
up with changes in unpublished development branches. Additionaly, it is
meant for utilities that the test harness relies on as well.

Bug: 155350825
Test: m compatibility-host-util-axt
Change-Id: I662f22a84ccb8b15d1750087c4feb12eff49865c
2 files changed