Restore view state for cells from redundant fs file change event

[rebornix]

Originally posted by in #153708 (comment)

As in the demo/gif in #153708, when we receive a content change event which contains no real model change, we still reset the model and lost all view states, which will trigger a flicker when the editor has horizontal scrollbars.

We should avoid the handling of such "redundant" file change events.

[rebornix]

Verification:

• Open a notebook file in VS Code
• Select some text in a cell editor
• Open terminal, touch file.ipynb to trigger a file change event
• Make sure the cell editor selection doesn't change