Extensible "Create Project" project type list

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).

Start by locating the current hardcoded Create Java Project type list and reviewing how package.json contributes extension metadata. Define the contribution data for extension ID, label, command ID, and optional arguments, then verify that another extension can provide a project type and that the Create Project list invokes it correctly.