Add autoclick shortcut to a11y autoclick settings

Add a shortcut row that toggles floating icon and pops edit
shortcut type dialog.

Screencast:
 - autoclick indicator flag on:
   go/njiwntmwmjuwnzu2ote1mnw2m2nhmzflzi0znq
 - autoclick indicator flag off:
   go/screenshot-anpqrzv6ewplyjs

Bug: 397719419
Test: Manually verified on test devices
Flag: com.android.server.accessibility.enable_autoclick_indicator
Change-Id: I5f0b51adfaea5c3f8b077af07f34f61d78cb34ac