Introduced ClassCheckNode, a Truffle node to specialize the check for mono/polymorphic SendNodes

This node was introduced to avoid code invalidation caused by complex type checks in the normal `classOfReceiver(.)` and `Types.getClassOf` methods.

So, this node uses 'AST' specialization to reduce the complexity of the necessary check on the fast path.

[TODO-REPORT: describe approach and reasoning behind it]

Signed-off-by: Stefan Marr <git@stefan-marr.de>