Core: Fix core-common to use node-fetch

[ndelangen]

Closes #

What I did

I don't know how this has gone unnoticed.

core-common is a node package, but it seems to use fetch without any place where it's imported; meaning it's from a global. Node 16 does not ship with fetch build-in.

How to test

Ran into this here:
https://github.com/chromaui/addon-visual-tests

It's using auto-refs, that's likely how this code-path gets executed?

Checklist

• Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests)
• Make sure to add/update documentation regarding your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Maintainers

• If this PR should be tested against many or all sandboxes,
  make sure to add the ci:merged or ci:daily GH label to it.
• Make sure this PR contains one of the labels below.

["cleanup", "BREAKING CHANGE", "feature request", "bug", "documentation", "maintenance", "dependencies", "other"]