Wholesale migration away from go-multierror into a custom multierror implementation that is fully compatible with cockroachdb/errors, prints all errors, can be introspected with Is, As, and friends, and more. The new MultiError type is only available as an interface.
Co-authored-by: Camden Cheek <camden@ccheek.com>
This adds a couple of small helpers to make working with errors.Ignore a
little easier. Now, if you just want to ignore a certain error type,
instead of creating a function for it, you can just do something like
```
err = errors.Ignore(err, errors.IsPred(context.Canceled))
```
This adds the new helper function `Ignore` to our `errors` package. This
allows us to ignore errors based on a given predicate function in a way
that takes into account aggregated errors in MultiError. It recursively
unwraps to multierrors an filters out all child errors that match the
predicate.
