Deprecate errors/merrors

[SuperQ]

Now that Go 1.20 supports multi-error handling, it's probably time to deprecate and remove the merrors package. Similar, pkg/errors has been archived and this should probably be deprecated in favor of the stdlib errors package.

[bwplotka]

Thanks!

We have to revisit merrors indeed, but https://github.com/efficientgo/core/tree/main/errors pkg exists on purpose, as stdlib error wrapping is not perfect (not really type safe, no stack trace). Explained a bit more in my book 🙃