Fix sending service notifications

[xPaw]

• Fix notification servicemethods not working
• Add SendNotification and deprecate SendMessage(..., true)

This was broken in #1036, ServiceMethodSendToClient was not the correct call. Notifications are sent by Steam by not setting the source jobid.

This logic can be verified by looking at the new chat's javascript. it has SendMsg/SendNotification on service transport. SendMsg uses SendMsgAndAwaitResponse which sets the jobid_source.

@Netshroud which notification message did you test?

[JustArchi]

I helped 🙂.

[JustArchi]

Tested SendNotification() with below code as of 84f4049 - works.

		CFriendMessages_AckMessage_Notification request = new() {
			steamid_partner = steamID,
			timestamp = timestamp
		};

		UnifiedFriendMessagesService.SendNotification(x => x.AckMessage(request));

[JustArchi]

Also tested SendMessage() that was isNotification: false, also works.

🚢 it