REGTESTS: sample_fetches: test the raw TLS hello fetches

REGTESTS: sample_fetches: test the raw TLS hello fetches

req.ssl_hello_type, req.ssl_ver, req.ssl_ec_ext, req.ssl_st_ext and
res.ssl_hello_type had no coverage, nor had the deprecated
req_ssl_hello_type, req_ssl_ver, req_ssl_sni and rep_ssl_hello_type
aliases. They parse the raw buffer of a TCP proxy without any SSL data
layer, so the handshake messages are crafted by hand with sendhex the
same way the other ClientHello tests do, and a server answers each of
them with a ServerHello so that the response side is covered too.

Three ClientHellos are used: one carrying server_name, supported_groups
and an empty session ticket, one carrying a session ticket with data
and no supported_groups, and one carrying a single unrelated extension
so that req.ssl_st_ext reports its documented zero.