Add a tutorial on writing a simple blocking QUIC client

Add a tutorial on writing a simple blocking QUIC client

This tutorial only covers a single stream client at this stage. A future
PR will cover adding multi-stream support.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Hugo Landau <hlandau@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/21204)