Proper webpack https support

What does this Merge Request do and why?

Proper webpack https support

Rather than configuring the webpack dev server to work with https, we simply reverse proxy the dev server web socket through nginx.

We can already provide DEV_SERVER_PUBLIC_ADDR (which we need for Gitpod, as it runs on a different domain). Reusing this env variable makes it much easier to configure the webpack dev server.

Merge Request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise Issue to follow-up.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.