Ensure proper sequencing of notebook cell edits

[DonJayamanne]

Problem
Assume we generate a single text edit for a single cell in a notebook
Sequence of messages emitted is as follows

1. Empty NotebookEdit [] (URI = Notebook URI `file://sample.ipynb`)
2. Text Edit for Cell URI  (URI = Cell URI= `vscode-notebook-cell://sample.ipynb?w234`)
3. NotebookEdito isDone=true (URI = Notebook URI `file://sample.ipynb`)
```

What happens with the the messages is as follows:
UpdateContent of `changeModel.ts` stores the messages in the following manner
_responseParts = [
    { 
        kind: 'notebookEditGroup',
        uri: <Notebook URI>,
        edits: [[]],
        done: true
    },
    { 
        kind: 'textEditGroup',
        uri: <Cell URI>,
        edits: [[]],
        done: true
    },
]

And they get process as follows in handleResponseParts of chatEditingServiceImpl:

1. First process the first empty element in `notebookEditGroup`
2. After we're done processing all `edits` in the `notebookEditGroup`, we then move onto `done`.
3. At this point `done = true` for `notebookEditGroup`, hence the ModifiedFileEntry gets the `done` and we complete the stream and resolve chat session, etc.

NOTE: None of the cell edits have been handled.
I.e. the order is now wrong, the text edits were sent before the `notebook.done = true`.

4. Now we process the notebook cell edit operations.
However this is out of sequence.

I think the problem lies with the fact that the textEdits are not treated as part of the notebookEditGroup.
Ideally they should be part of that so that they are processes in order.
Or we bring the knowledge of notebook Cell Edits into this area and look at the Uris and do something else to ensure any text edits for a cell URI that belong to an existing notebookgroup must be processed first and the notebookGroup.done must be processed after all other textEditGroup... feels icky..

@jrieken @connor4312 /cc

[DonJayamanne]

Text edits belonging to a notebook must belong to notebookGroup
This way the order is preserved and its clear these text edits belong to notebooks.

[connor4312]

When you call startStreamingEdits, it sequences operations based on the resource URI passed in. Maybe the way you want to do this is to call that for cell URIs individually or something, and then update the ChatEditingService to keep track of them.

[DonJayamanne]

it sequences operations based on the resource URI passed in. Maybe the way you want to do this is to call that for cell URIs individually or something, and then update the ChatEditingService to keep track of them.

Sorry not following you here.
@connor4312 Sounds like you are proposing a different implementation, please could you elaborate, thanks

[connor4312]

Looking more, I think this should work fine :) I might do a pass later and see if I can get rid of the any cast (we had one there before, so not something you need to clean in this PR unless you want to)

[jrieken]

@connor4312 @DonJayamanne Can we align these and just have pushEdits(uri, edits) because all these call _acceptEdits