Update LAST_DECL_ATTR and add verification to ensure it is always updated

Author: meg-gupta

include/swift/AST/DeclAttr.def

@@ -510,7 +510,7 @@ DECL_ATTR(lifetime, Lifetime,
   OnAccessor | OnConstructor | OnFunc | OnSubscript | LongAttribute | ABIBreakingToAdd | ABIStableToRemove | APIBreakingToAdd | APIStableToRemove,
   161)
 
-LAST_DECL_ATTR(Unsafe)
+LAST_DECL_ATTR(Lifetime)
 
 #undef DECL_ATTR_ALIAS
 #undef CONTEXTUAL_DECL_ATTR_ALIAS

lib/AST/Attr.cpp

@@ -39,6 +39,7 @@
 using namespace swift;
 
 #define DECL_ATTR(_, Id, ...) \
+  static_assert(DeclAttrKind::Id <= DeclAttrKind::Last_DeclAttr); \
   static_assert(IsTriviallyDestructible<Id##Attr>::value, \
                 "Attrs are BumpPtrAllocated; the destructor is never called");
 #include "swift/AST/DeclAttr.def"