Optimize Container Tabs from Excessive Request Checks

Currently the extension opts for an approach where every single request is checked for whether it should be delegated to a container tab, but this is not strictly necessary. If you're already inside of a container tab which belongs to an application, e.g. MuWire, then there is usually no need to check again(The exception being i2psnark, which can display web pages which can attempt to fetch resources from a server under attacker control). There may be other situations where it makes sense to limit the amount of checking that we do in firefox-default tabs but this is much more complicated(Fortunately, none of the other frequently-performed-actions are applied to firefox-default tabs so it may be less of an issue there,