Include whether a mode is active in the subtext of dialog tiles

Active modes with trigger descriptions now show "On * <Trigger Desc>", similarly as Settings does. This way not only the color is different between an active and inactive mode tile.

(This doesn't fix the non-annoucement in Talkback, but gets us closer).

Bug: 359845144
Test: atest ModesDialogViewModelTest
Flag: android.app.modes_ui
Change-Id: I34f22ab824f7e230f07e8623f44b796fd8219e23