Check getShowSoftInputOnFocus() for stylus input

When there is stylus input on a text editor which doesn't support
handwriting, a toast error message is displayed and the soft keyboard is
shown. However, if the text editor has setShowSoftInputOnFocus(false),
then this should be respected by not showing the soft keyboard.

Bug: 363180475
Test: atest StylusHandwritingTest
Flag: com.android.text.flags.handwriting_unsupported_show_soft_input_fix
Change-Id: I906fe51586d173dee37395b63c33632e94af6af4