Show Quick pick if multiple extensions register `notebook.format` code action providers.

              later we can show a quick pick.

_Originally posted by @rebornix in https://github.com/microsoft/vscode/pull/212750#discussion_r1604049009_

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Tie quick pick into `notebook.defaultFormatter` setting. Quick Pick should display all the extension ID's and can likely leverage the DefaultFormatter class the same as the setting to populate