Fix test failures(bug 268231685) on TV targets

Fix bug in both InputMethodManagerServiceWindowGainedFocusTest and AutoShowTest by taking screen size into consideration, because IMMS would do auto-show in ImeVisibilityStateComputer#computeState() on large screen devices.

Bug: 268231685
Test: atest com.android.server.inputmethod.InputMethodManagerServiceWindowGainedFocusTest
Change-Id: Ib8cc36f65386591740c571bba8d6edd41d2373f2