Support interactive formatter settings wizard

[CsCherrYY]

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

[rgrunber]

I think moving these into vscode-java would be a step in the right direction as we could also use a similar approach for the Java compiler options https://github.com/eclipse/eclipse.jdt.ls/wiki/Language-Server-Settings-&-Capabilities#java-compiler-options . We wouldn't need the preview capability there though.