Enable watch rotary scroll on IME Switcher menu

This enables scrolling on the IME swithcer menu using the watch rotary
input, which requires focus on the scrollable view.

Flag: android.view.inputmethod.ime_switcher_revamp
Bug: 311791923
Test: flash on watch; adb shell input keyevent KEYCODE_SYM
Change-Id: Ifc87b5d145351e2076f2bbd60cf4eb9f1e682783