Could not auto close unsaved editor when delete

The newly added "delete" feature #343 works well when we try to delete unchanged files. However, if we try to delete file with unsaved changes, the editor will not be closed and will looks like below:

This is not consistent with native file explorer's behavior and may also cause user lose their changes before deletion. However, this part is hard to fix due to API limitation, since many needed functions are encapsulated within the implementation of VS Code built-in commands. If microsoft/vscode#107566 could be solved, we can fix this problem easily.

issue #343 の削除機能から始め、VS Code 拡張機能で未保存の変更があるファイルの削除を再現します。API の制限を理解するために microsoft/vscode#107566 を読みます。完了条件は、未保存の変更を危険にさらすことなく、エディターがネイティブのファイル エクスプローラーの動作と一貫して閉じることです。