multi: use the "errors" package everywhere

Replace all usages of the "github.com/go-errors/errors" and
"github.com/pkg/errors" packages with the standard lib's "errors"
package. This ensures that error wrapping and `errors.Is` checks will
work as expected.

lnwire/onion_error.go

@@ -9,7 +9,6 @@ import (
 	"io"
 
 	"github.com/davecgh/go-spew/spew"
-	"github.com/go-errors/errors"
 	"github.com/lightningnetwork/lnd/fn/v2"
 	"github.com/lightningnetwork/lnd/tlv"
 )
@@ -1513,7 +1512,7 @@ func makeEmptyOnionError(code FailCode) (FailureMessage, error) {
 		return &FailInvalidBlinding{}, nil
 
 	default:
-		return nil, errors.Errorf("unknown error code: %v", code)
+		return nil, fmt.Errorf("unknown error code: %v", code)
 	}
 }