Swap out `node-fetch` for `undici`

[rmunn]

Describe the problem

#4934 had a checklist step "swap out node-fetch for undici, which is more standards compliant (though I think we're blocked on nodejs/undici#1262)". nodejs/undici#1262 has just been closed via nodejs/undici#1469, so it may be time to look again at swapping out node-fetch, at least once nodejs/undici#1469 makes its way into an actual Node release.

Describe the proposed solution

Swap out node-fetch for undici as described in #4934 (comment)

Alternatives considered

No response

Importance

would make my life easier

Additional Information

This should allow us to make progress on #3419 as well (see #4934 (comment)).

[OttoHatt]

I believe this'll be blocked by #5109 (cloudflare wrangler also uses Undici for requests).

[rmunn]

I believe this'll be blocked by #5109 (cloudflare wrangler also uses Undici for requests).

#5109 is marked as fixed by #5116, which has been released in next.346. I can't confirm that the fix works on Cloudflare as I don't have any Cloudflare sites set up at the moment; @OttoHatt, can you confirm that it works?

[OttoHatt]

yes! on the newest version, #5109 is fixed.