Support for asdf

What does this Merge Request do?

This MR adds support for asdf by:

• Adds .tool-versions with Ruby, Golang and Node.js etc versions
• Adds asdf-setup make target

With the .tool-versions in place, one can run the following to install asdf plugins and needed versions:

$ make asdf-setup

Merge Request checklist

• Tests added for new functionality. If not, please raise Issue to follow-up.
• This change is backward compatible. If not, please include steps to communicate to our users.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.