Request errors handling revamp
LibResilient has to handle request errors better. It needs to be smart about displaying the original 404 page from the original domain, and otherwise needs to show some form of a plugin call stack or other explanation if a request failed.
Currently when a request fails (for example, due to 404 error, or because integrity check fails, or...), an internal "request failed" page is displayed by the website. This is not very helpful when debugging issues, and at the same time this is confusing to potential users.