Let the system dialog honor FLAG_ALT_FOCUSABLE_IM

This CL adds a new condition to needsRelativeLayeringToIme() so that
system dialogs having FLAG_ALT_FOCUSABLE_IM is correctly placed above
the IME window.

Bug: 260536813
Test: atest CtsAutoFillServiceTestCases:android.autofillservice.cts.saveui.SimpleSaveActivityTest#testAutoFillOneDatasetAndSave_usingUiAutomatorOnly
Change-Id: I795462274f5e845e6af60aea3f4fb858c0e383a8