Sandbox more input-related configs instead of fontScale with SCM

Due to a careless mistake, fontScale is unintentionally sandboxed
with SCM with I9876fccda2e08a9cc97e4963290c6f05516f90f6, this is
not needed as fontScale is global (not per-display). Our intention
was to sandbox keyboard instead. (keyboardHidden,
hardkeyboardHidden, and navigationHidden could also be updated
with this although it's even more rare, so we sandbox them too
jsut in case.)

Also in the newly added unit test, KEYBOARD_TYPE_ALPHABETIC needs
to be set via setKeyboardType(), not via setSources(), which is
why the error above wasn't catched.

Flag: com.android.window.flags.enable_size_compat_mode_improvements_for_connected_displays
Bug: 399749909
Test: SizeCompatTest#testFixedScreenConfigurationWhenMovingToDisplay
Change-Id: I6df448c8530a6a357a40597774783351768ab9ec