New extensions can be sent in a certificate request

New extensions can be sent in a certificate request

Normally we expect a client to send new  extensions in the ClientHello,
which may be echoed back by the server in subsequent messages. However the
server can also send a new extension in the certificate request message to
be echoed back in a certificate message

Fixes #16632

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16634)