all: use math/rand/v2 more

Updates #11058

Signed-off-by: Maisem Ali <maisem@tailscale.com>

tstest/integration/testcontrol/testcontrol.go

@@ -14,7 +14,7 @@ import (
 	"io"
 	"log"
 	"maps"
-	"math/rand"
+	"math/rand/v2"
 	"net/http"
 	"net/http/httptest"
 	"net/netip"
@@ -774,7 +774,7 @@ func (s *Server) serveMap(w http.ResponseWriter, r *http.Request, mkey key.Machi
 		go panic(fmt.Sprintf("bad map request: %v", err))
 	}
 
-	jitter := time.Duration(rand.Intn(8000)) * time.Millisecond
+	jitter := rand.N(8 * time.Second)
 	keepAlive := 50*time.Second + jitter
 
 	node := s.Node(req.NodeKey)

tstest/jsdeps/jsdeps.go

@@ -14,7 +14,7 @@ import (
 	_ "encoding/json"
 	_ "fmt"
 	_ "log"
-	_ "math/rand"
+	_ "math/rand/v2"
 	_ "net"
 	_ "strings"
 	_ "time"

tstest/natlab/natlab.go

@@ -14,7 +14,7 @@ import (
 	"encoding/base64"
 	"errors"
 	"fmt"
-	"math/rand"
+	"math/rand/v2"
 	"net"
 	"net/netip"
 	"os"
@@ -566,7 +566,7 @@ func (m *Machine) pickEphemPort() (port uint16, err error) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	for tries := 0; tries < 500; tries++ {
-		port := uint16(rand.Intn(32<<10) + 32<<10)
+		port := uint16(rand.IntN(32<<10) + 32<<10)
 		if !m.portInUseLocked(port) {
 			return port, nil
 		}