Support interactive formatter settings wizard

Currently we use Java: Open Java Formatter Settings to open the formatter settings profile (xml file), once the profile exists, the command will open that file in xml scheme, and it's not such friendly for users to change the configurations, since they don't know the exact meaning of each setting id.

vscode-java-pack extension now supports Java: Open Java Formatter Settings with Preview, which uses a custom editor to provide interactive editing experience of formatting settings.

It would be great if we merge the two entries into one and put the implementation into vscode-java repository, the interactive custom editor can replace currently plain xml to provide better experience, and we still remain a switch to open the profile in plain xml scheme for advanced users.

any thoughts? @fbricon @rgrunber @snjeza

vscode-java に存在する formatter-settings コマンドを vscode-java-pack のインタラクティブな実装と比較し、それぞれのコマンドおよびカスタムエディターのエントリポイントから調査を始めます。エントリポイントを統合し、インタラクティブなフォーマッター編集を提供し、上級ユーザー向けにプロファイルをプレーン XML として開く方法を維持できれば完了です。