Add priv-app allow-listing for unbundled chooser.

These two permissions are required for the most basic
ChooserActivity flows (as determined by runtime exceptions
during prototyping). Without this allow-listing, the
unbundled chooser's intent resolvers fail to register at
startup, and the device boot-loops.

Among the privileges that might require allow-listing,
these two in particular were sufficient for showing a
basic Chooser UI and launching the user-selected target.
More complex Chooser flows may turn out to require
additional permissions later on.

Test: manual testing as described above, but requires
several local-only changes to exercise the flow, and
this CL has to be the first to go in (but has no
side-effects of its own).

Change-Id: I6a24a46a91199e8b3fb643f047a9b9412b19eb8d