Correctly handle a retransmitted ClientHello

Correctly handle a retransmitted ClientHello

If we receive a ClientHello and send back a HelloVerifyRequest, we need
to be able to handle the scenario where the HelloVerifyRequest gets lost
and we receive another ClientHello with the message sequence number set to
0.

Fixes #18635

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Hugo Landau <hlandau@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/18654)

(cherry picked from commit 81926c91567cd5d11eec38b9980438f45b276d72)