Migrate to internal node implementation of fetch

[brendandburns]

We are going to remove the node-fetch dependency and move to node's internal implementation.

[cjihrig]

I think this might also resolve #2127 since native fetch has a keepalive option, which node-fetch does not.

EDIT: This is probably wrong. The keepalive in the fetch spec is something different.

[k8s-triage-robot]

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/lifecycle stale

[mstruebing]

/remove-lifecycle stale

[k8s-triage-robot]

The Kubernetes project currently lacks enough contributors to adequately respond to all issues.

This bot triages un-triaged issues according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
• After 30d of inactivity since lifecycle/rotten was applied, the issue is closed

You can:

• Mark this issue as fresh with /remove-lifecycle stale
• Close this issue with /close
• Offer to help out with Issue Triage

Please send feedback to sig-contributor-experience at kubernetes/community.

/lifecycle stale