Remove github.com/pkg/errors and replace with std library version

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.

fs/operations/lsjson.go

@@ -2,11 +2,12 @@ package operations
 
 import (
 	"context"
+	"errors"
+	"fmt"
 	"path"
 	"strings"
 	"time"
 
-	"github.com/pkg/errors"
 	"github.com/rclone/rclone/backend/crypt"
 	"github.com/rclone/rclone/fs"
 	"github.com/rclone/rclone/fs/hash"
@@ -118,14 +119,14 @@ func newListJSON(ctx context.Context, fsrc fs.Fs, remote string, opt *ListJSONOp
 	if opt.ShowEncrypted {
 		fsInfo, _, _, config, err := fs.ConfigFs(fsrc.Name() + ":" + fsrc.Root())
 		if err != nil {
-			return nil, errors.Wrap(err, "ListJSON failed to load config for crypt remote")
+			return nil, fmt.Errorf("ListJSON failed to load config for crypt remote: %w", err)
 		}
 		if fsInfo.Name != "crypt" {
 			return nil, errors.New("The remote needs to be of type \"crypt\"")
 		}
 		lj.cipher, err = crypt.NewCipher(config)
 		if err != nil {
-			return nil, errors.Wrap(err, "ListJSON failed to make new crypt remote")
+			return nil, fmt.Errorf("ListJSON failed to make new crypt remote: %w", err)
 		}
 	}
 	features := fsrc.Features()
@@ -237,19 +238,19 @@ func ListJSON(ctx context.Context, fsrc fs.Fs, remote string, opt *ListJSONOpt,
 		for _, entry := range entries {
 			item, err := lj.entry(ctx, entry)
 			if err != nil {
-				return errors.Wrap(err, "creating entry failed in ListJSON")
+				return fmt.Errorf("creating entry failed in ListJSON: %w", err)
 			}
 			if item != nil {
 				err = callback(item)
 				if err != nil {
-					return errors.Wrap(err, "callback failed in ListJSON")
+					return fmt.Errorf("callback failed in ListJSON: %w", err)
 				}
 			}
 		}
 		return nil
 	})
 	if err != nil {
-		return errors.Wrap(err, "error in ListJSON")
+		return fmt.Errorf("error in ListJSON: %w", err)
 	}
 	return nil
 }