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.

lib/file/preallocate_windows.go

@@ -4,12 +4,12 @@
 package file
 
 import (
+	"fmt"
 	"os"
 	"sync"
 	"syscall"
 	"unsafe"
 
-	"github.com/pkg/errors"
 	"golang.org/x/sys/windows"
 )
 
@@ -63,13 +63,13 @@ func PreAllocate(size int64, out *os.File) error {
 		uintptr(3), // FileFsSizeInformation
 	)
 	if e1 != nil && e1 != syscall.Errno(0) {
-		return errors.Wrap(e1, "preAllocate NtQueryVolumeInformationFile failed")
+		return fmt.Errorf("preAllocate NtQueryVolumeInformationFile failed: %w", e1)
 	}
 
 	// Calculate the allocation size
 	clusterSize := uint64(fsSizeInfo.BytesPerSector) * uint64(fsSizeInfo.SectorsPerAllocationUnit)
 	if clusterSize <= 0 {
-		return errors.Errorf("preAllocate clusterSize %d <= 0", clusterSize)
+		return fmt.Errorf("preAllocate clusterSize %d <= 0", clusterSize)
 	}
 	allocInfo.AllocationSize = (1 + uint64(size-1)/clusterSize) * clusterSize
 
@@ -85,7 +85,7 @@ func PreAllocate(size int64, out *os.File) error {
 		if e1 == syscall.Errno(windows.ERROR_DISK_FULL) || e1 == syscall.Errno(windows.ERROR_HANDLE_DISK_FULL) {
 			return ErrDiskFull
 		}
-		return errors.Wrap(e1, "preAllocate NtSetInformationFile failed")
+		return fmt.Errorf("preAllocate NtSetInformationFile failed: %w", e1)
 	}
 
 	return nil
@@ -104,7 +104,7 @@ func SetSparse(out *os.File) error {
 	var bytesReturned uint32
 	err := syscall.DeviceIoControl(syscall.Handle(out.Fd()), FSCTL_SET_SPARSE, nil, 0, nil, 0, &bytesReturned, nil)
 	if err != nil {
-		return errors.Wrap(err, "DeviceIoControl FSCTL_SET_SPARSE")
+		return fmt.Errorf("DeviceIoControl FSCTL_SET_SPARSE: %w", err)
 	}
 	return nil
 }