forward innerException's error code to retryable HttpRequestException (…

…#89963)

If we are doing a retry because of a protocol error, or some other HttpIOException, we should forward the error code to the retryable HttpRequestException

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/Http2Connection.cs

@@ -2205,7 +2205,7 @@ internal void Trace(int streamId, string message, [CallerMemberName] string? mem
 
         [DoesNotReturn]
         private static void ThrowRetry(string message, Exception? innerException = null) =>
-            throw new HttpRequestException(HttpRequestError.Unknown, message, innerException, RequestRetryType.RetryOnConnectionFailure);
+            throw new HttpRequestException((innerException as HttpIOException)?.HttpRequestError ?? HttpRequestError.Unknown, message, innerException, RequestRetryType.RetryOnConnectionFailure);
 
         private static Exception GetRequestAbortedException(Exception? innerException = null) =>
             innerException as HttpIOException ?? new IOException(SR.net_http_request_aborted, innerException);