Exposes affordance names through content provider.

We need the names so we can build the summary for the settings item in
the settings app. For example, if the user picks home controls for the
left slot and wallet for the right slot, we want to show "Home, Wallet"
on the settings screen.

Bug: 256662519
Test: Unit tests expanded. Manually verified with the next CL on the
chain to verify that it works end-to-end.

Change-Id: I4cf67b118340ba264c481ab79a67ad45d6620ff0