Flicker test for PiP and launcher shelf height

PipMovesInAllApps was intended to test the PiP window movement when the
shelf height of Launcher changes and breaks with the recent `Device
search` feature that opening all-apps in Launcher triggers both IME and
shelf height change.

Since PipKeyboardTest has covered PiP movement with IME, reimplement
this by launching a new app instead of going to all-apps and also rename
this test for its intention.

Bug: 184050344
Test: atest WMShellFlickerTests:PipShelfHeightTest
Change-Id: I102ea95e6e91c9707b73587282702b868eb705fb