edit_history: Update simulated edit history entries in frontend.
edit_history: Update simulated edit history entries in frontend.

Updates the simulated edit history entries that are saved when
`update_messages` events are received for the modern data
structure on the server for `message.edit_history` entries.

Also cleans up a misnamed field in said entries, `edited_by`.

rht/zulip,kou/zulip,andersk/zulip,kou/zulip,zulip/zulip,kou/zulip,zulip/zulip,zulip/zulip,kou/zulip,andersk/zulip,zulip/zulip,zulip/zulip,andersk/zulip,andersk/zulip,rht/zulip,andersk/zulip,zulip/zulip,kou/zulip,rht/zulip,rht/zulip,zulip/zulip,kou/zulip,kou/zulip,rht/zulip,rht/zulip,andersk/zulip,andersk/zulip,rht/zulip