elang/optimizer: Introduce validator for |IfNode|, |IfFalseNode| and |IfTrueNode|.
elang/optimizer: Introduce validator for |IfNode|, |IfFalseNode| and |IfTrueNode|.

eval1749/elang,eval1749/elang,eval1749/elang,eval1749/elang,eval1749/elang