Fixes #6547
Reported by staticcheck 2022.1.2 (v0.3.2) See: staticcheck.io
This is possible now that we no longer support go1.12 and brings rclone into line with standard practices in the Go world. This also removes errors.New and errors.Errorf from lib/errors and prefers the stdlib errors package over lib/errors.
This changes the Config interface so that it returns an error.