download_strategy: ignore query strings when parsing resolved URLs

[Bo98]

An alternative to #13108 for fixing Homebrew/homebrew-cask#121725, but I think it makes sense to make both changes.

We currently parse query strings https://example.com/download.php?file=foo-1.0.tar.gz to extract the file extension.

This is not always correct. Sometimes you have scenarios like https://example.com/file=foo-1.0.tar.gz?host=elsewhere.com where it'll think elsewhere.com is the basename.

It's impossible to tell really how a URL should be parsed, so what I've done is alter the behaviour of URL parsing in the scenario where we've already followed redirects and checked headers. This means we have checked for and did not find a Content-Disposition so we are safe to follow what browsers do: take the basename, ingoring the query string.

Keep the original behaviour for the "dumber" scan-the-unresolved-URL case (i.e. the URL direct from the formula and cask), which is less likely to have crazy query strings at the end of the URL.

[BrewTestBot]

Review period skipped due to critical label.

[MikeMcQuaid]

No strong views on which approach we take.