switch to new sync/atomic helpers in go1.19 (#728)

These new helpers make the code a lot cleaner. I confirmed that the
simple helpers like `atomic.Int64` don't add any extra overhead as they
get inlined by the compiler. `atomic.Pointer` adds an extra method call
as it no longer gets inlined, but we aren't using these on the hot path
so it is probably okay.

control.go

@@ -5,7 +5,6 @@ import (
 	"net"
 	"os"
 	"os/signal"
-	"sync/atomic"
 	"syscall"
 
 	"github.com/sirupsen/logrus"
@@ -219,7 +218,7 @@ func copyHostInfo(h *HostInfo, preferredRanges []*net.IPNet) ControlHostInfo {
 	}
 
 	if h.ConnectionState != nil {
-		chi.MessageCounter = atomic.LoadUint64(&h.ConnectionState.atomicMessageCounter)
+		chi.MessageCounter = h.ConnectionState.messageCounter.Load()
 	}
 
 	if c := h.GetCert(); c != nil {