cloud: fix usage of CombineErrors

Previously, nodelocal and cloud contained CombineErrors calls that were
passing the secondary error as the first argument. This is undesirable
because only the first argument to CombineErrors is part of the causal
error chain.

The instance of this in WriteFile was uncovered by a fault injection
test. An injected error was being unexpectedly retried because Close was
failing with a context cancelled error.

Release note: none
Epic: CRDB-53946

Author: jeffswenson

pkg/blobs/local_storage.go

@@ -84,7 +84,7 @@ func (l localWriter) Close() error {
 
 	syncErr := l.f.Sync()
 	closeErr := l.f.Close()
-	if err := errors.CombineErrors(closeErr, syncErr); err != nil {
+	if err := errors.CombineErrors(syncErr, closeErr); err != nil {
 		return err
 	}
 	// Finally put the file to its final location.

pkg/cloud/cloud_io.go

@@ -454,7 +454,7 @@ func WriteFile(ctx context.Context, dest ExternalStorage, basename string, src i
 	_, err = io.Copy(w, src)
 	if err != nil {
 		cancel()
-		return errors.CombineErrors(w.Close(), err)
+		return errors.CombineErrors(err, w.Close())
 	}
 	return errors.Wrap(w.Close(), "closing object")
 }