Use onSecondaryContainer color in IME switcher

The item text and checkmark image were always using the onSurface color
role (matching the dialog background), however the selected item's
background is using the secondaryContainer color role.

This updates the resources to use the correct color roles based on the
item selection status.

Flag: android.view.inputmethod.ime_switcher_revamp
Test: show IME Switcher menu in different contrast modes
Bug: 361057000
Change-Id: Iec24ae6394596dccc4395df58a94ae3d1415d312