Update c/image for golang.org/x/exp

> go get github.com/containers/image/v5@main
> go mod tidy && go mod vendor

This updates c/image with a new version of x/exp.
That package has changed API in an incompatible way,
so just bumping x/exp (as in https://github.com/containers/skopeo/pull/2060 )
would break Skopeo builds.

This updates both c/image and x/exp in lockstep (and nothing
needs updating in Skopeo itself for the x/exp breakage).

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

vendor/github.com/vbatts/tar-split/archive/tar/reader.go

@@ -7,7 +7,6 @@ package tar
 import (
 	"bytes"
 	"io"
-	"io/ioutil"
 	"strconv"
 	"strings"
 	"time"
@@ -140,7 +139,7 @@ func (tr *Reader) next() (*Header, error) {
 			continue // This is a meta header affecting the next header
 		case TypeGNULongName, TypeGNULongLink:
 			format.mayOnlyBe(FormatGNU)
-			realname, err := ioutil.ReadAll(tr)
+			realname, err := io.ReadAll(tr)
 			if err != nil {
 				return nil, err
 			}
@@ -334,7 +333,7 @@ func mergePAX(hdr *Header, paxHdrs map[string]string) (err error) {
 // parsePAX parses PAX headers.
 // If an extended header (type 'x') is invalid, ErrHeader is returned
 func parsePAX(r io.Reader) (map[string]string, error) {
-	buf, err := ioutil.ReadAll(r)
+	buf, err := io.ReadAll(r)
 	if err != nil {
 		return nil, err
 	}
@@ -916,7 +915,7 @@ func discard(tr *Reader, n int64) error {
 		}
 	}
 
-	copySkipped, err = io.CopyN(ioutil.Discard, r, n-seekSkipped)
+	copySkipped, err = io.CopyN(io.Discard, r, n-seekSkipped)
 out:
 	if err == io.EOF && seekSkipped+copySkipped < n {
 		err = io.ErrUnexpectedEOF