Introduce CustomChoosers API for NFC resolver.

This includes both the `CustomChoosers` "helper API" that builds the
"customized chooser" intent, as well as the framework's default
fulfillment for that intent in `NfcResolverActivity`. (Note the
`NfcResolverActivity` could move to a different component later, but
the `CustomChoosers` "helper" is the real client-facing API.)

Test: CtsNfcResolverDeviceTest (see ag/25300036)
Bug: 268089816
Change-Id: I72d917a73f354784ae53c3c5b5e7e66964482f80