http: assert parser.consume argument's type

Unchecked argument conversion in Parser::Consume crashes node
in an slightly undesirable manner - 'unreachable code' in parser.

Make sure we validate the incoming type at the earliest point.

PR-URL: https://github.com/nodejs/node/pull/12288
Fixes: https://github.com/nodejs/node/issues/12178


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Alexey Orlenko <eaglexrlnk@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Refael Ackermann <refack@gmail.com>