[Arith] Allow vector expressions in IntSet::operator(PrimExpr)

Since these are tracked when lowering expressions, should allow
post-vectorization expressions.

To maintain previous behavior, this only applies when using the
automatically tracked `Map<Var, IntSet> dom_map_`.  If an explicit
domain map is passed, the previous behavior of raising an error for
vectorized expressions still occurs.

src/arith/int_set.cc

@@ -511,7 +511,7 @@ class IntSetAnalyzer::Impl {
   }
 
   IntSet Eval(const PrimExpr& expr) const {
-    return IntervalSetEvaluator(analyzer_, GetCurrentBounds()).Eval(expr);
+    return IntervalSetEvaluator(analyzer_, GetCurrentBounds(), true).Eval(expr);
   }
 
   void Bind(const Var& var, const Range& range, bool allow_override) {