Consolidate use of errors

[jcaamano]

As follows:

• Replaced all equivalent uses of github.com/pkg/errors for standard library errors
• Replaced the uses of github.com/pkg/errors Wrapf for fmt.Errorf. The need for the stack trace that Wrapf brings seems arbitrary
• Replaced the uses of the standard library errors Join, as well as k8s aggregate errors, with our own implementation which works similarly to standard library's but formats the concatenation as the k8s aggregate errors separating with commas rather than new lines which is an inconvenience. When compared to k8s aggregate errors, our implementation is simpler catering to our needs and complies fully with current wrapping mechanism whereas the former does not support 'errors.As'

[tssurya]

I think this was a really nice cleanup, however unless we add some section here: https://ovn-kubernetes.io/developer-guide/developer/ for developers I get this feeling in no time we might go back to using different things in different spots. Just putting what's in the commit message under a sub heading is good enough for the docs, that way next time we can just point people to Best Practices or Coding Style for OVN-Kubernetes etc.. will be nice to have a section there.