feat: make UndiciErrors reliable to instanceof

[Uzlopak]

fixes #3987

This is basically the same approach we use in @fastify/errors

This relates to...

Rationale

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• I have read and agreed to the Developer's Certificate of Origin
• Tested
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[mcollina]

lgtm

[mcollina]

this should be backporrted to v6

[github-actions]

The backport to v6.x failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-v6.x v6.x
# Navigate to the new working tree
cd .worktrees/backport-v6.x
# Create a new branch
git switch --create backport-4472-to-v6.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 5f256afdcb49d0502bc61056ad49a829814b25cb
# Push it to GitHub
git push --set-upstream origin backport-4472-to-v6.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-v6.x

Then, create a pull request where the base branch is v6.x and the compare/head branch is backport-4472-to-v6.x.

[metcoder95]

@Uzlopak can you try to backport it?

[Uzlopak]

i will try to backport it. Currently doing some other stuff locally. ;)