VULN-141859: Normalize request path when using access rules

With the previous changes made to normalize request paths, we faced some issues:

* Regressions in Next.js route groups: https://github.com/cloudflare/cloudflared/issues/1719
* WordPress trailing slashes: https://github.com/cloudflare/cloudflared/issues/1717

This PR attempts to fix a vulnerability regarding un-normalized request paths using a different approach:
instead of mutating `req.URL.Path` before forwarding to the origin, we compute a cleaned path used only for
ingress rule selection, leaving the original request completely untouched. This separates the security classification decision from request proxying.

Since this can be a breaking change, we are adding it disabled by default and will only enable it in future releases.