REGTESTS: ssl: test the ssl_fc_* and ssl_bc_* connection fetches

REGTESTS: ssl: test the ssl_fc_* and ssl_bc_* connection fetches

The existing SSL tests cover the certificate fetches (ssl_f_*, ssl_c_*
and ssl_s_*) but almost none of the ones describing the connection
itself. This test chains a clear frontend to an SSL backend and an SSL
frontend so that both families are read on the same exchange: the
ssl_bc_* ones from the client side of the SSL connection and the
ssl_fc_* ones from its server side, which lets the two be compared.

It covers ssl_bc, ssl_bc_alpn, ssl_bc_cipher, ssl_bc_protocol,
ssl_bc_alg_keysize, ssl_bc_use_keysize, ssl_bc_sni, ssl_bc_is_resumed,
ssl_bc_session_id, ssl_bc_unique_id, ssl_bc_client_random,
ssl_bc_server_random, ssl_bc_session_key, and on the frontend side
ssl_fc_protocol, ssl_fc_protocol_hello_id, ssl_fc_alg_keysize,
ssl_fc_use_keysize, ssl_fc_has_sni, ssl_fc_has_crt, ssl_fc_crtname,
ssl_fc_has_early, ssl_fc_session_id, ssl_fc_unique_id,
ssl_fc_client_random, ssl_fc_server_random, ssl_fc_session_key, plus
the captured ClientHello fetches ssl_fc_cipherlist_str, _hex, _bin,
_xxh, ssl_fc_eclist_bin, ssl_fc_ecformats_bin, ssl_fc_extlist_bin and
ssl_fc_sigalgs_bin.

A second pair of listeners pins TLSv1.3 to reach what only exists
there: ssl_fc_supported_versions_bin and the four traffic secrets plus
the exporter secret, on both ends.

The capture buffer is sized so that the whole ClientHello fits,
otherwise the extension lists which follow the cipher list are
silently reported as empty.