all: migrate code from netaddr.FromStdAddr to Go 1.18

With caveat https://github.com/golang/go/issues/53607#issuecomment-1203466984
that then requires a new wrapper. But a simpler one at least.

Updates #5162

Change-Id: I0a5265065bfcd7f21e8dd65b2bd74cae90d76090
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

ipn/ipnlocal/peerapi.go

@@ -493,8 +493,8 @@ func (pln *peerAPIListener) serve() {
 			logf("peerapi: unexpected RemoteAddr %#v", c.RemoteAddr())
 			continue
 		}
-		ipp, ok := netaddr.FromStdAddr(ta.IP, ta.Port, "")
-		if !ok {
+		ipp := netaddr.Unmap(ta.AddrPort())
+		if !ipp.IsValid() {
 			logf("peerapi: bogus TCPAddr %#v", ta)
 			c.Close()
 			continue