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>

version/print.go

@@ -7,11 +7,10 @@ import (
 	"fmt"
 	"runtime"
 	"strings"
-
-	"tailscale.com/types/lazy"
+	"sync"
 )
 
-var stringLazy = lazy.SyncFunc(func() string {
+var stringLazy = sync.OnceValue(func() string {
 	var ret strings.Builder
 	ret.WriteString(Short())
 	ret.WriteByte('\n')