util/cmpx: remove code that's in the stdlib now

The cmpx.Compare function (and associated interface) are now available
in the standard library as cmp.Compare. Remove our version of it and use
the version from the standard library.

Updates #cleanup

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: I4be3ac63d466c05eb7a0babb25cb0d41816fbd53

cmd/derper/depaware.txt

@@ -193,7 +193,7 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
         golang.org/x/time/rate                                       from tailscale.com/cmd/derper+
         bufio                                                        from compress/flate+
         bytes                                                        from bufio+
-        cmp                                                          from slices
+        cmp                                                          from slices+
         compress/flate                                               from compress/gzip+
         compress/gzip                                                from internal/profile+
         container/list                                               from crypto/tls+

cmd/netlogfmt/main.go

@@ -25,6 +25,7 @@
 package main
 
 import (
+	"cmp"
 	"encoding/base64"
 	"encoding/json"
 	"flag"
@@ -45,7 +46,6 @@ import (
 	"github.com/go-json-experiment/json/jsontext"
 	"tailscale.com/types/logid"
 	"tailscale.com/types/netlogtype"
-	"tailscale.com/util/cmpx"
 	"tailscale.com/util/must"
 )
 
@@ -155,7 +155,7 @@ func printMessage(msg message) {
 		slices.SortFunc(traffic, func(x, y netlogtype.ConnectionCounts) int {
 			nx := x.TxPackets + x.TxBytes + x.RxPackets + x.RxBytes
 			ny := y.TxPackets + y.TxBytes + y.RxPackets + y.RxBytes
-			return cmpx.Compare(ny, nx)
+			return cmp.Compare(ny, nx)
 		})
 		var sum netlogtype.Counts
 		for _, cc := range traffic {

cmd/tailscale/cli/exitnode.go

@@ -4,6 +4,7 @@
 package cli
 
 import (
+	"cmp"
 	"context"
 	"errors"
 	"flag"
@@ -17,7 +18,6 @@ import (
 	xmaps "golang.org/x/exp/maps"
 	"tailscale.com/ipn/ipnstate"
 	"tailscale.com/tailcfg"
-	"tailscale.com/util/cmpx"
 )
 
 var exitNodeCmd = &ffcli.Command{
@@ -228,7 +228,7 @@ func filterFormatAndSortExitNodes(peers []*ipnstate.PeerStatus, filterBy string)
 // by location.Priority, in order of highest priority.
 func sortPeersByPriority(peers []*ipnstate.PeerStatus) {
 	slices.SortStableFunc(peers, func(a, b *ipnstate.PeerStatus) int {
-		return cmpx.Compare(b.Location.Priority, a.Location.Priority)
+		return cmp.Compare(b.Location.Priority, a.Location.Priority)
 	})
 }