all: use Go 1.20's bytes.Clone

Updates #7123
Updates #6257 (more to do in other repos)

Change-Id: I073e2a6d81a5d7fbecc29caddb7e057ff65239d0
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

derp/derp_test.go

@@ -126,7 +126,7 @@ func TestSendRecv(t *testing.T) {
 					if m.Source.IsZero() {
 						t.Errorf("zero Source address in ReceivedPacket")
 					}
-					recvChs[i] <- append([]byte(nil), m.Data...)
+					recvChs[i] <- bytes.Clone(m.Data)
 				}
 			}
 		}(i)

derp/derphttp/derphttp_test.go

@@ -4,6 +4,7 @@
 package derphttp
 
 import (
+	"bytes"
 	"context"
 	"crypto/tls"
 	"net"
@@ -102,7 +103,7 @@ func TestSendRecv(t *testing.T) {
 				case derp.PeerGoneMessage:
 					// Ignore.
 				case derp.ReceivedPacket:
-					recvChs[i] <- append([]byte(nil), m.Data...)
+					recvChs[i] <- bytes.Clone(m.Data)
 				}
 			}
 		}(i)