Fix several viewport issues (#1045)

* Fix some FOV calculation viewport issues:
-Avoid calculating FOV if we've got an invalid viewport
-Don't override game mode FOV, let the active camera components manage it instead

* Fix viewport font positioning

This updates code in a few places to respect an API change/fix made to AtomFont - also switched the default value of m_virtual800x600ScreenSize to false as it's really behavior you want to opt into

* Don't activate CameraComponentController when in the Editor / not in game mode

Gems/Camera/Code/Source/CameraComponentController.cpp

@@ -240,7 +240,9 @@ namespace Camera
         CameraBus::Handler::BusConnect();
         CameraNotificationBus::Broadcast(&CameraNotificationBus::Events::OnCameraAdded, m_entityId);
 
-        if (m_config.m_makeActiveViewOnActivation)
+        // Activate our camera if we're running from the launcher or Editor game mode
+        // Otherwise, let the Editor keep managing the active camera
+        if (m_config.m_makeActiveViewOnActivation && (!gEnv || !gEnv->IsEditor() || gEnv->IsEditorGameMode()))
         {
             MakeActiveView();
         }