WebGUI::Session::Http should go away (#11647)

Move logic out of WebGUI::Session::HTTP and into WebGUI::Session::Response /
::Request; deprecate more functions; change references in core to use
$session->response instead; fix tests that broke because of the change but
not one that merely generate the deprecated warning because I want to know
that the proxying of depricated methods is working.  These can be changed later.

lib/WebGUI/Content/Maintenance.pm

@@ -47,7 +47,7 @@ The content handler for this package.
 sub handler {
     my $session = shift;
     if ($session->setting->get("specialState") eq "upgrading") {
-        $session->http->sendHeader;
+        $session->response->sendHeader;
         open my $fh, '<', $session->config->get('maintenancePage');
         my $output = do { local $/; <$fh> };
         close $fh;