onError implementation (GraphQL v17)

[benjie]

codex-performed port of #4364 to the GraphQL v17 branch

git checkout on-error
git diff 16.x.x > on-error.diff

Then codex with prompt:

on-error.diff contains a diff from 16.x.x to on-error, implementing the new onError request argument. Implement these same changes against the current branch, adjusting for the new features in 17.x.x as necessary. At the end npm run test should pass, as should npm run lint.

Then telling codex off a bit for cheating... ;)

[vercel]

@benjie is attempting to deploy a commit to the The GraphQL Foundation Team on Vercel.

A member of the Team first needs to authorize it.

[benjie]

Took a while to go through and fix all the shortcuts codex took, but I think we're there.