Include module list in global-config node when exporting flows

[knolleary]

Part of #4597

When exporting a flow from the editor (via Ctrl-E, or deploying to runtime), the editor will now scan the nodes being exported and if any come from modules other than node-red, it will include a global-config node in the export (or update an existing one) to include a modules object:

For example:

    {
        "id": "501579b48496ccb7",
        "type": "global-config",
        "modules": {
            "node-red-node-daemon": "0.2.1"
        }
    }

Keeping this PR in draft as we need to do the import side of it as well.

[johnwyles]

big ups on this one ^