Wrong formatting edits applied when running "Format Notebook"

[roblourens]

Environment data

• VS Code version: 1.60 insiders
• Extension version (available under the Extensions sidebar): v2021.8.1159798656
• OS and version: macOS

Steps

• Open a notebook
• Right click on a cell editor and run "Format Notebook"
• The same edit gets applied to all cells

I don't know but I suspect the problem is with using .fileName for these temp files. That doesn't include the cell, so when we call this for all cells, it probably reuses the same temp file

https://vscode.dev/github/microsoft/vscode-python/blob/7adee50afc79ad0875044a78e1158249859f200b/src/client/formatters/baseFormatter.ts#L128-L128

Downstream microsoft/vscode#131342

[karthiknadig]

duplicate of #16980