MINOR: quic: Enable early data at SSL session level (aws-lc)

MINOR: quic: Enable early data at SSL session level (aws-lc)

This patch impacts only the haproxy build against aws-lc TLS stack (USE_OPENSSL_AWSLC).

Implement qc_set_quic_early_data_enabled() new function to enable
early data at session level. To make QUIC O-RTT work, a context string
must be set calling SSL_set_quic_early_data_context(). This is a
subset of the encoded transport parameters which is used for this.
Note that some application level settings should be also added (TODO).

This patch is required to make 0-RTT work for haproxy builds against aws-lc.