spanner: ErrRowNotFound is not compatible with apierror

[golemiso]

I found that the latest release has a type compatibility issue.
All of the errors returned from spanner api were compatible with apierror, but with this fix (#10405), errors instantiated as apierror are now overwritten with ErrRowNotFound.

This modification violates #5169

Additional context

Started after upgrading to v1.64.0.

[golemiso]

I found a workaround.

I was getting an apierror by the code below and returns non apierror after v1.64.0:

var apiErr *apierror.APIError
if !errors.As(err, &apiErr) {
	return err
}
return apiErr

I found using apierror.FromError works fine before and after v1.64.0:

apiErr, ok := apierror.FromError(err)
if !ok {
	return err
}
return apiErr