`x-unknown` is used as a placeholder for "no content-type" in the har.
We should not send it to the browser, because it is meaningfully
different from not sending `Content-Type` header. For example, Chromium
refuses to interpret stylesheets served with `x-unknown` content type.
Fixes https://github.com/microsoft/playwright-java/issues/1651.
Fixes#24144.
Previously, we only matched by url, which confuses GET and HEAD requests
where the latter is usually zero-sized.
Also make sure that resources are sorted by their monotonicTime, since
that's not always the case in the trace file, where they are sorted by
the "response body retrieved" time.
