Make views_mus_unittests and views_mus_interactive_ui_tests use ws2

Make test_ws implement ServiceFactory and package the ui service.
Bind a ws2::WindowService instance to requests for the ui service.
Bind test WindowTreeHostFactory requests in WindowService's registry.
Have the test suites use test_ws + ui services instead of test_wm.

Add a TestGpuInterfaceInterfaceProvider with stub binding functions.
(that and an EventInjector registration placeholder prevent crashes)

Move shadow elevation property registration to ws2::WindowService.

Disable some broken mus-only tests, early return if IsMus from some others.
Remove the old ws service_unittests (catalog conflict packaging ui service)

Bug: 855609
Test: Automated, no regressions.
Change-Id: I58f65551c9c0e1c734ed4ac752b5219ecbead0db
Reviewed-on: https://chromium-review.googlesource.com/1138749
Commit-Queue: Michael Wasserman <msw@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576310}
16 files changed