Go v1.20 Update for multi error

[mvndaai]

Go added a errors.Join that allows joining errors. Together. This causes a problem with Unwrap because it can now return an array instead of just one error. This can lose fields that are joined together because doing unwrap will just unwrap the first one in the list.

golang/go#53435 (comment)

[mvndaai]

Needs something similar to what go error package does
https://cs.opensource.google/go/go/+/refs/tags/go1.21.1:src/errors/wrap.go;l=117-132

switch x := err.(type) {
case interface{ Unwrap() error }:
	err = x.Unwrap()
	if err == nil {
		return false
	}
case interface{ Unwrap() []error }:
	for _, err := range x.Unwrap() {
		if As(err, target) {
			return true
		}
	}
	return false
default:
	return false
}

[mvndaai]

This should be a breadth first search so we still get the deepest fields.

[mvndaai]

Released in https://github.com/mvndaai/ctxerr/releases/tag/v0.13.0