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

比较 vscode-java 中现有的 formatter-settings 命令与 vscode-java-pack 中的交互式实现，从它们的命令和自定义编辑器入口点入手。完成的标准是整合这些入口点，提供交互式格式化器编辑，并保留一种将配置文件作为纯 XML 打开的方式，供高级用户使用。