Use std library errors

[rowanseymour]

Remove github.com/pkg/errors which is dead like in nyaruka/gocommon#128 and nyaruka/goflow#1258

[rowanseymour]

can use find and replace with regex for some of this...

errors\.Wrap\(err, "([^"]+)"\) > fmt.Errorf("$1: %w", err)

[rowanseymour]

Even better....

errors\.Wrapf?\(err, "([^"]+)"(.*)\)$

fmt.Errorf("$1: %w"$2, err)

[rowanseymour]

BUT... errors.Wrap and errors.Wrapf return nil if passed a nil error... fmt.Errorf doesn't... so you gotta look for cases where we were relying on that. You can find some with ^\treturn fmt\.Errorf\( which are lines returning an err which aren't indented in an if

[norkans7]

Yes, I suspect that is causing issues in backends/rapidpro I will update that part in a second PR