Notebook variables view polish

[amunger]

following up on #203058

• notebook variables view should handle very long lists #203060
• variable provider for built-in view should display better value information vscode-jupyter#15056
• Persist variable expansion state through variable update events in notebook variables view #203067
• Don't show the notebook variable view when not applicable #203068
• A string with newlines is not colored red #203231
• Show longer variable preview on hover #203237

[davidanthoff]

Could #204031 be added to this list?

[brad-griffin]

Dictionaries appear to be limited to showing only the first 100 keys. Are there any plans to expand this similar to long lists or allow more keys to be shown?

[amunger]

it looks like pydebug has a configurable limit of 500, we could follow that same convention here. Would that work for your use case?

[brad-griffin]

Yes, that should cover it!