dispose saved text model with wrong view type

[amunger]

fix #208016

as mentioned in this comment, when we save as on a notebook model, we leave the newly created model orphaned, to be picked up by the editor that is about to be created with the new resource.
In the case of saving an interactive window, we are saving the model with the interactive viewtype, since the model factory in the interactive working copy has that viewtype, but the new editor will open with the notebook viewtype.

We can fix this by just disposing the new model that we create, and the editor will resolve another model with the correct viewtype.

[amunger]

It feels like it would be better to just choose the viewtype while saving, but I don't see a clean way to pipe that through the current code flow, but maybe there is a way to shortcut the text model creation that I'm missing.

[bpasero]

Isn't the model disposed automatically once the editor closes the old one and opens the new one? There should not be a reference anymore after saving, or?

[amunger]

The path used to save is not the same as the one the open editor was using (similar to saving an unsaved notebook)

The open editor is /interactive-1.interactive with view type 'interactive
A new text model is created just to save for {saved-path}.ipynb with view type 'interactive'
A new editor is opened for {saved-path}.ipynb with view type 'notebook'