all: use various net/netip parse funcs directly

Mechanical change with perl+goimports.

Changed {Must,}Parse{IP,IPPrefix,IPPort} to their netip variants, then
goimports -d .

Finally, removed the net/netaddr wrappers, to prevent future use.

Updates #5162

Change-Id: I59c0e38b5fbca5a935d701645789cddf3d7863ad
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

net/packet/icmp6_test.go

@@ -5,17 +5,17 @@
 package packet
 
 import (
+	"net/netip"
 	"testing"
 
-	"tailscale.com/net/netaddr"
 	"tailscale.com/types/ipproto"
 )
 
 func TestICMPv6PingResponse(t *testing.T) {
 	pingHdr := ICMP6Header{
 		IP6Header: IP6Header{
-			Src:     netaddr.MustParseIP("1::1"),
-			Dst:     netaddr.MustParseIP("2::2"),
+			Src:     netip.MustParseAddr("1::1"),
+			Dst:     netip.MustParseAddr("2::2"),
 			IPProto: ipproto.ICMPv6,
 		},
 		Type: ICMP6EchoRequest,