Unify dialer implementations

Instead of having several dialer implementations, leave only one in
`pkg/dialer` and call it from `pkg/ttrpcutil`, `runtime/v(1|2)/shim`
which had their own

Closes #3471.

Signed-off-by: Kiril Vladimiroff <kiril@vladimiroff.org>

pkg/dialer/dialer_windows.go

@@ -19,21 +19,13 @@ package dialer
 import (
 	"net"
 	"os"
-	"syscall"
 	"time"
 
 	winio "github.com/Microsoft/go-winio"
 )
 
 func isNoent(err error) bool {
-	if err != nil {
-		if oerr, ok := err.(*os.PathError); ok {
-			if oerr.Err == syscall.ENOENT {
-				return true
-			}
-		}
-	}
-	return false
+	return os.IsNotExist(err)
 }
 
 func dialer(address string, timeout time.Duration) (net.Conn, error) {