Extensible "Create Project" project type list

[sdedic]

I have a request similar to #713, but more generic: that the Create Project list of project types could be extensible - and other extensions could contribute to it. Adding explicitly project types with their extension IDs and commands centrally into vscode-java-dependency does not scale well, as many extensions that support a certain technology could offer preconfigured java project templates, or "wizards" to create boilerplate projects. In the long run, opening integration in the Create Java Project can offer a smooth user experience.

The same data as with the current hardcoded list could be contributed through package.json by other extensions: extension ID, label and command ID, and the Java Dependency extension would then define argument(s) that will be passed to the creation command (if any).