[nfc] add variadic is for types

Author: kavon

include/swift/AST/Types.h

@@ -614,6 +614,11 @@ class alignas(1 << TypeAlignInBits) TypeBase
     static_assert(!isSugaredType<T>(), "isa desugars types");
     return isa<T>(getDesugaredType());
   }
+
+  template <typename First, typename Second, typename... Rest>
+  bool is() {
+    return is<First>() || is<Second, Rest...>();
+  }
 
   template <typename T>
   T *castTo() {