util/uniq,types/lazy,*: delete code that's now in Go std

sync.OnceValue and slices.Compact were both added in Go 1.21.

cmp.Or was added in Go 1.22.

Updates #8632
Updates #11058

Change-Id: I89ba4c404f40188e1f8a9566c8aaa049be377754
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

ipn/localapi/debugderp.go

@@ -4,6 +4,7 @@
 package localapi
 
 import (
+	"cmp"
 	"context"
 	"crypto/tls"
 	"encoding/json"
@@ -81,7 +82,7 @@ func (h *Handler) serveDebugDERPRegion(w http.ResponseWriter, r *http.Request) {
 		client *http.Client = http.DefaultClient
 	)
 	checkConn := func(derpNode *tailcfg.DERPNode) bool {
-		port := firstNonzero(derpNode.DERPPort, 443)
+		port := cmp.Or(derpNode.DERPPort, 443)
 
 		var (
 			hasIPv4 bool
@@ -89,7 +90,7 @@ func (h *Handler) serveDebugDERPRegion(w http.ResponseWriter, r *http.Request) {
 		)
 
 		// Check IPv4 first
-		addr := net.JoinHostPort(firstNonzero(derpNode.IPv4, derpNode.HostName), strconv.Itoa(port))
+		addr := net.JoinHostPort(cmp.Or(derpNode.IPv4, derpNode.HostName), strconv.Itoa(port))
 		conn, err := dialer.DialContext(ctx, "tcp4", addr)
 		if err != nil {
 			st.Errors = append(st.Errors, fmt.Sprintf("Error connecting to node %q @ %q over IPv4: %v", derpNode.HostName, addr, err))
@@ -98,7 +99,7 @@ func (h *Handler) serveDebugDERPRegion(w http.ResponseWriter, r *http.Request) {
 
 			// Upgrade to TLS and verify that works properly.
 			tlsConn := tls.Client(conn, &tls.Config{
-				ServerName: firstNonzero(derpNode.CertName, derpNode.HostName),
+				ServerName: cmp.Or(derpNode.CertName, derpNode.HostName),
 			})
 			if err := tlsConn.HandshakeContext(ctx); err != nil {
 				st.Errors = append(st.Errors, fmt.Sprintf("Error upgrading connection to node %q @ %q to TLS over IPv4: %v", derpNode.HostName, addr, err))
@@ -108,7 +109,7 @@ func (h *Handler) serveDebugDERPRegion(w http.ResponseWriter, r *http.Request) {
 		}
 
 		// Check IPv6
-		addr = net.JoinHostPort(firstNonzero(derpNode.IPv6, derpNode.HostName), strconv.Itoa(port))
+		addr = net.JoinHostPort(cmp.Or(derpNode.IPv6, derpNode.HostName), strconv.Itoa(port))
 		conn, err = dialer.DialContext(ctx, "tcp6", addr)
 		if err != nil {
 			st.Errors = append(st.Errors, fmt.Sprintf("Error connecting to node %q @ %q over IPv6: %v", derpNode.HostName, addr, err))
@@ -117,7 +118,7 @@ func (h *Handler) serveDebugDERPRegion(w http.ResponseWriter, r *http.Request) {
 
 			// Upgrade to TLS and verify that works properly.
 			tlsConn := tls.Client(conn, &tls.Config{
-				ServerName: firstNonzero(derpNode.CertName, derpNode.HostName),
+				ServerName: cmp.Or(derpNode.CertName, derpNode.HostName),
 				// TODO(andrew-d): we should print more
 				// detailed failure information on if/why TLS
 				// verification fails
@@ -166,7 +167,7 @@ func (h *Handler) serveDebugDERPRegion(w http.ResponseWriter, r *http.Request) {
 			addr = addrs[0]
 		}
 
-		addrPort := netip.AddrPortFrom(addr, uint16(firstNonzero(derpNode.STUNPort, 3478)))
+		addrPort := netip.AddrPortFrom(addr, uint16(cmp.Or(derpNode.STUNPort, 3478)))
 
 		txID := stun.NewTxID()
 		req := stun.Request(txID)
@@ -292,13 +293,3 @@ func (h *Handler) serveDebugDERPRegion(w http.ResponseWriter, r *http.Request) {
 	//   issued in the first place, tell them specifically that the
 	// 	 cert is bad not just that the connection failed.
 }
-
-func firstNonzero[T comparable](items ...T) T {
-	var zero T
-	for _, item := range items {
-		if item != zero {
-			return item
-		}
-	}
-	return zero
-}