Bug 1665614 - Make mozilla::Result work with non-copyable/non-param error types. r=emilio,jandem

Among other things, there were some misuses of std::forward, and
GenericErrorResult was (presumably accidentally) instatiated with
references as the template argument type, e.g. const nsresult&,
which circumvented the check for not calling it with NS_OK in
ResultExtensions.h

Differential Revision: https://phabricator.services.mozilla.com/D90561

netwerk/protocol/res/ExtensionProtocolHandler.cpp

@@ -891,7 +891,7 @@ void ExtensionProtocolHandler::NewSimpleChannel(nsIURI* aURI,
         nsresult rv = origChannel->AsyncOpen(listener);
         if (NS_FAILED(rv)) {
           simpleChannel->Cancel(NS_BINDING_ABORTED);
-          return RequestOrReason(rv);
+          return Err(rv);
         }
         return RequestOrReason(origChannel);
       });