all: use Go 1.26 things, run most gofix modernizers

I omitted a lot of the min/max modernizers because they didn't
result in more clear code.

Some of it's older "for x := range 123".

Also: errors.AsType, any, fmt.Appendf, etc.

Updates #18682

Change-Id: I83a451577f33877f962766a5b65ce86f7696471c
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/k8s-operator/egress-services-readiness_test.go

@@ -9,7 +9,6 @@ import (
 	"fmt"
 	"testing"
 
-	"github.com/AlekSi/pointer"
 	"go.uber.org/zap"
 	appsv1 "k8s.io/api/apps/v1"
 	corev1 "k8s.io/api/core/v1"
@@ -145,9 +144,9 @@ func setEndpointForReplica(pg *tsapi.ProxyGroup, ordinal int32, eps *discoveryv1
 	eps.Endpoints = append(eps.Endpoints, discoveryv1.Endpoint{
 		Addresses: []string{p.Status.PodIPs[0].IP},
 		Conditions: discoveryv1.EndpointConditions{
-			Ready:       pointer.ToBool(true),
-			Serving:     pointer.ToBool(true),
-			Terminating: pointer.ToBool(false),
+			Ready:       new(true),
+			Serving:     new(true),
+			Terminating: new(false),
 		},
 	})
 }