System->Unbundled, AppPrediction availability bit.

The current logic in ChooserActivity depends on checking
for the presence of a particular AppPredictionService
component in AiAi, but that check always fails in the
unbundled Chooser. Instead, only check when we're
running on the system side, and hand off the bit in an
extra on the delegation intent.

Test: trivial (needs other changes for meaningful behavior)
Bug: 206831012
Change-Id: I86919d962ac25fc1a4dd4a25d672d400abc64ff2