MINOR: http: add <need_eot> to trailers parsing function

MINOR: http: add <need_eot> to trailers parsing function

Adds an extra argument to http_trailers_to_htx() to specify if EOT block
is necessary. Most of this times this will be set to true by callers.
However, it is necessary to skip it if caller does not want to report
EOM immediately after.

For now, every parsers set this new argument to true. This will change
for HTTP/3 parser as FIN can be received later.