Alyways use AbstractLeftTuple instead of LeftTuple (Fix the secondary super cache problem in Drools)

To avoid checks against the LeftTuple interface, I’ve replaced every usage of LeftTuple with AbstractLeftTuple. This problem isn’t triggered with AbstractClass and in the code there is no advantage in having such an interface. I suggest in the actual PR to remove the interface altogether and just use the AbstractClass.

The description of the problem is here