Move OperationCompressor functionallity to a method on editor.model

[scofalik]

📝 Provide a description of the improvement

https://github.com/ckeditor/ckeditor5-engine/blob/master/src/model/operation/operationfactory.js

Here's OperationFactory in its full glory. Which is not a lot of glory.

I'd like to move this functionallity to a place, which will be reachable from editor. For example, editor.model.createOperationFromJson().

The case here is that we'd like to introduce a plugin, which is needed if we want to let users upload their editor builds to CS. This plugin needs OperationFactory. We'd like that plugin to be automatically added on a CS side, so the user does not need to add this plugin on their own to their build. So, we need to add it to .extraPlugins. But it is not possible, because OperationFactory needs to be imported and this raises duplicate modules error.

If we have editor.model.createOperationFromJson() we would be able to make build uploading easier for our customers.

Two additional things that we need to take under consideration:

1. I am a little hestitant of having this method in docs, but what can you do 🤷‍♂️. The thing is that it is quite low level stuff and it probably should never be used by integration code or 3rd party plugins. But, yeah, 🤷‍♂️.
2. We need to check if importing all the operations won't lead to circular deps problem.