[Physical Keyboard] Fix bug for Mouse key page

Add default Locale to get keycode for mouse key.

Bug: 387152641
Bug: 386907528
Flag: com.android.settings.keyboard.keyboard_and_touchpad_a11y_new_page_enabled
Test: atest packages/apps/Settings/tests/robotests/src/com/android/settings/inputmethod
Change-Id: I8cc4a08449c13b426ffa24ddc29fd16407b064c8