all: rename NetworkLock functions/types to TailnetLock

To avoid breaking downstream code, add deprecated aliases for all the
old names.

Updates tailscale/corp#37904

Change-Id: I86d0b0d7da371946440b181c665448f91c3ef8d2
Signed-off-by: Alex Chan <alexc@tailscale.com>

cmd/tl-longchain/tl-longchain.go

@@ -45,7 +45,7 @@ func main() {
 	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
 	defer cancel()
 
-	st, err := lc.NetworkLockStatus(ctx)
+	st, err := lc.TailnetLockStatus(ctx)
 	if err != nil {
 		log.Fatalf("could not get Tailnet Lock status: %v", err)
 	}