test: check that --insecure-http-parser works

Test that using --insecure-http-parser will disable validation of
invalid characters in HTTP headers.

See:
- https://github.com/nodejs/node/pull/30567

Backport-PR-URL: https://github.com/nodejs/node/pull/30471
PR-URL: https://github.com/nodejs/node/pull/31253


Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>