Add 4 CUJs using explicit trace assertions.

We will let this run for a week and evaluate the reliability of this new
method against the current equivalent tests that are constantly failing.

If this proves to be reliable, then we'll need to refactor this class to make it extensible to other CUJs. (b/408170368)

Flag: EXEMPT, test improvements
Bug: 408170846
Test: atest WMShellFlickerTestsDesktopMode:com.android.wm.shell.flicker.OpenAppFromTaskbarLandscapeExplicitTest and others
Change-Id: I0262133d0fd1392574fbe07793b5163981b1686a