[NFC][Clang] Adopt simplified getTrailingObjects in Decl/StmtOpenACC (llvm#140087)

Adopt non-templated and array-ref returning forms of
`getTrailingObjects` in DeclOpenACC and StmtOpenACC. Also use
std::uninitialized_contruct_n to make the code a little concise.

Author: jurahul

clang/include/clang/AST/DeclOpenACC.h

@@ -73,10 +73,8 @@ class OpenACCDeclareDecl final
 
   OpenACCDeclareDecl(unsigned NumClauses)
       : OpenACCConstructDecl(OpenACCDeclare) {
-    std::uninitialized_value_construct(
-        getTrailingObjects<const OpenACCClause *>(),
-        getTrailingObjects<const OpenACCClause *>() + NumClauses);
-    setClauseList(getTrailingObjects<const OpenACCClause *>(NumClauses));
+    std::uninitialized_value_construct_n(getTrailingObjects(), NumClauses);
+    setClauseList(getTrailingObjects(NumClauses));
   }
 
   OpenACCDeclareDecl(DeclContext *DC, SourceLocation StartLoc,
@@ -85,10 +83,9 @@ class OpenACCDeclareDecl final
       : OpenACCConstructDecl(OpenACCDeclare, DC, OpenACCDirectiveKind::Declare,
                              StartLoc, DirLoc, EndLoc) {
     // Initialize the trailing storage.
-    llvm::uninitialized_copy(Clauses,
-                             getTrailingObjects<const OpenACCClause *>());
+    llvm::uninitialized_copy(Clauses, getTrailingObjects());
 
-    setClauseList(getTrailingObjects<const OpenACCClause *>(Clauses.size()));
+    setClauseList(getTrailingObjects(Clauses.size()));
   }
 
 public:
@@ -117,10 +114,8 @@ class OpenACCRoutineDecl final
 
   OpenACCRoutineDecl(unsigned NumClauses)
       : OpenACCConstructDecl(OpenACCRoutine) {
-    std::uninitialized_value_construct(
-        getTrailingObjects<const OpenACCClause *>(),
-        getTrailingObjects<const OpenACCClause *>() + NumClauses);
-    setClauseList(getTrailingObjects<const OpenACCClause *>(NumClauses));
+    std::uninitialized_value_construct_n(getTrailingObjects(), NumClauses);
+    setClauseList(getTrailingObjects(NumClauses));
   }
 
   OpenACCRoutineDecl(DeclContext *DC, SourceLocation StartLoc,
@@ -134,9 +129,8 @@ class OpenACCRoutineDecl final
     assert(LParenLoc.isValid() &&
            "Cannot represent implicit name with this declaration");
     // Initialize the trailing storage.
-    llvm::uninitialized_copy(Clauses,
-                             getTrailingObjects<const OpenACCClause *>());
-    setClauseList(getTrailingObjects<const OpenACCClause *>(Clauses.size()));
+    llvm::uninitialized_copy(Clauses, getTrailingObjects());
+    setClauseList(getTrailingObjects(Clauses.size()));
   }
 
 public: