[Clang] Fix handling of Max from getValueRange(...) in IntExprEvaluator::VisitCastExpr(...)

This is a follow-up to D130058 to fix how we handle the Max value we obtain from
getValueRange(...) in IntExprEvaluator::VisitCastExpr(...) which in the case of
an enum that contains an enumerator with the max integer value will overflow by
one.

The fix is to decrement the value of Max and use slt and ult for comparison Vs
sle and ule.`

Differential Revision: https://reviews.llvm.org/D130811