Keep hold of a reference to the user SSL in QUIC

Keep hold of a reference to the user SSL in QUIC

In some cases a QUIC SSL_CONNECTION object needs to get hold of a reference
to the original SSL object as created by the user. We should keep a
reference to it.

Reviewed-by: Viktor Dukhovni <viktor@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/25931)

(cherry picked from commit 6612799fb51eea3ddd0f077a76d01db873d43df9)