[HLSL] Implement constant expression evaluator for HLSL splat cast #125766
Description
See PR for Implementation of this cast #118992
Add support to handle the new cast in the constant expression evaluator (clang/lib/AST/ExprConstant.cpp)
Support to handle this cast should be added to:
- VectorExprEvaluator::VisitCastExpr
- RecordExprEvaluator::VisitCastExpr
- ArrayExprEvaluator::VisitCastExpr (There is currently no such function but I believe it should be added).