Add setHasTopUi(true) during cross-activity and cross-task predictive back

Bug: 350934546
Flag: com.android.window.flags.predictive_back_system_anims
Test: Manual, i.e. verifying that wmshell.main shows up on big cpu instead of mid/little cpu during predictive back animation in perfetto traces
Change-Id: I52377fc2814a8b0d9fbfa417d2c72d209af588ee