BUG/MINOR: http-htx: Don't normalize emtpy path for OPTIONS requests

BUG/MINOR: http-htx: Don't normalize emtpy path for OPTIONS requests

When the scheme-based normalization is performed, an empty path is
normalized to "/". But as stated in RFC9110#4.2.3, this must not be applied
on OPTIONS requests.

So let's fix the issue by adding a test on the method.

Thanks to @zhanhb for the bug report and the analysis.

This patch should fix the issue #3352. It must be backported as far as 3.0.