Revert "Revert "[TypeSystem] Specialized method now contains a flag specifying the""

This reverts commit b758539431a287c3ad23f1911e07f72d939d928f.
Revert "Revert "Implemented better way to handle extension method invocations.""

This reverts commit c26f61e8133ce2558d93531bb771ffb0c3bb6ac7.
Revert "Revert "Implemented reduced method model.""

This reverts commit bdc1fde9d6266f60ffba84e0d227506b0bd37540.
Reduced extension methods are now always non static methods with
extension method flag set.