Let user select a version a `runtimeExecutable` path to specific node.js in Node Launch Configuration

WWD needs a NodeJS to run language servers, and also to execute NodeJS launch configurations. Currently, there's not much control over which NodeJS is used. You either have to set org.eclipse.wildwebdeveloper.nodeJSLocation in eclipse.ini or add NodeJS to your PATH. This isn't very flexible, and is problematic because I work on multiple projects that use different versions of NodeJS.

Today, I'm just setting nodeJSLocation and living with the fact that language servers are run with a different NodeJS than the projects are built with. And I'm using JSDT's NodeJS launch config to build the projects, since JSDT allows me to select which NodeJS I want.

It would be nice if WWD provided a workspace-level config option to set which NodeJS to use, and used the specified NodeJS to start language servers and to run NodeJS launch configs.

Start by tracing the existing org.eclipse.wildwebdeveloper.nodeJSLocation setting, language-server startup, and the NodeJS launch configuration. Done means a workspace-level Node.js selection is honored for both language servers and NodeJS launch configurations, including projects that use different Node.js versions.