Memory leak when reusing GrpcChannel on many clients about magiconion

[mayuki]

This problem is caused by the existence of a cache of methods inside GrpcChannel.
MagicOnionClient.Create generates a method each time it creates a client for the purpose of binding a serializer/marshaller.

MagicOnionClient has a method called WithOptions that returns a client with different options only. This client shares the same methods as the original client.

private static async Task Main(string[] args)
{
    // Connect to the server using gRPC channel.
    var channel = GrpcChannel.ForAddress("http://localhost:5000");
    var ci = channel.CreateCallInvoker();
    var client = MagicOnionClient.Create<IMyFirstService>(ci); // <-- Create a client only once.
    while (true)
    {
        var clientWithOptions = client.WithOptions(...); // <-- Create a client with new options here.
        var result = await clientWithOptions.SumAsync(123, 456);
        Debug.Assert(result == 123 + 456);
    }
}