Physical keyboard related options shouldn't be searchable when invisible

Physical keyboard options category is hidden when there is no hardware
keyboard. It's related preferences are hidden in this case. Hence those
preferences shouldn't be searchable.

Bug: 351047456
Test: manually search "bounce keys", "sticky keys" and "slow keys",
they're not searchable when invisible on Accessibility page
Test: atest
Flag: com.android.settings.accessibility.fix_a11y_settings_search

Change-Id: I1eb465dd34e59d856bb1fa7c06bc253971a8c8d0