types/ptr: deprecate ptr.To, use Go 1.26 new

Updates #18682

Change-Id: I62f6aa0de2a15ef8c1435032c6aa74a181c25f8f
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

util/syspolicy/setting/errors.go

@@ -5,8 +5,6 @@ package setting
 
 import (
 	"errors"
-
-	"tailscale.com/types/ptr"
 )
 
 var (
@@ -39,7 +37,7 @@ type ErrorText string
 
 // NewErrorText returns a [ErrorText] with the specified error message.
 func NewErrorText(text string) *ErrorText {
-	return ptr.To(ErrorText(text))
+	return new(ErrorText(text))
 }
 
 // MaybeErrorText returns an [ErrorText] with the text of the specified error,
@@ -51,7 +49,7 @@ func MaybeErrorText(err error) *ErrorText {
 	if err, ok := err.(*ErrorText); ok {
 		return err
 	}
-	return ptr.To(ErrorText(err.Error()))
+	return new(ErrorText(err.Error()))
 }
 
 // Error implements error.

util/syspolicy/setting/setting_test.go

@@ -9,7 +9,6 @@ import (
 	"testing"
 
 	"tailscale.com/types/lazy"
-	"tailscale.com/types/ptr"
 	"tailscale.com/util/syspolicy/internal"
 	"tailscale.com/util/syspolicy/pkey"
 )
@@ -138,7 +137,7 @@ func TestSettingDefinition(t *testing.T) {
 			if !tt.setting.Equal(tt.setting) {
 				t.Errorf("the setting should be equal to itself")
 			}
-			if tt.setting != nil && !tt.setting.Equal(ptr.To(*tt.setting)) {
+			if tt.setting != nil && !tt.setting.Equal(new(*tt.setting)) {
 				t.Errorf("the setting should be equal to its shallow copy")
 			}
 			if gotKey := tt.setting.Key(); gotKey != tt.wantKey {