typeahead [nfc]: Dedupe query_matches_person logic a bit.
typeahead [nfc]: Dedupe query_matches_person logic a bit.

I think this makes the flow a bit clearer: we always search
`.full_name`, and if emails are real then we also search the email.

zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip