Provide more information to the noti asst

And pass user sentiment from the assistant to listeners.

Not all of the information the assistant might want is provided
by systemui yet, but the hooks to do so have been added in this CL.

Bug: 63095540
Test: runtest systemui-notification, cts
Change-Id: I8194c065b7895d6013a40320e76eb62caab1263f