Revert "feat: add dm notify method (#660)"

[d-gubert]

This reverts commit dbb7e7c

It breaks quite a few conventions of the API - this makes the framework less intuitive, harder to find where things are (and it already is relatively difficult because we don't follow widespread dev patterns).

Having a method that sends a message on a Read accessor breaks the intended separation of concern of the API - and furthermore, the method has been added to the Notifier accessor, but it doesn't deal with a notification and rather sends a persistent message.

The IDirectMessage interface replaces the full room object with a three field object which does not conform to other points in the framework as well - and the concept of "Direct" in Rocket.Chat refers to a Room, not a Message.

A more flexible signature for the sendDirectMessage method would be to pass a message and a tuple of users. The method would then determine whether to create a new Direct room to send the message to or not.

To workaround the IPre... events limitation, we can start sending the IModify instance as a parameter to the event handler. It wasn't being sent before as a concern around performance, as this would give the app more surface to slow down whatever process they were being executed before (IPreMessageSent... potentially slowing down the process of sending messages, for instance). But considering the HTTP accessor is being passed as well, which apps can use to even call themselves in the server, we can argue on how effective the previous reasoning was.