Add patch set uploader to stream-events and hooks

Expose the uploader of each patch set to hooks and the stream-events
interface, so tools can report on it.

[sp: This is a squash of two changes that were very related.]
Change-Id: I7b6895a46c2e763eaf09e1aeb13878dd857a39c2
Change-Id: I4cab7aaa3ce26c317a5704451eb6576b03ab2980
3 files changed