[clang] [OpenACC][NFC] Add OpenACC Clause AST Nodes/infrastructure (PR #87675)

[Alexey Bataev via cfe-commits]

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@@ -47,6 +58,7 @@ class OpenACCConstructStmt : public Stmt {
 
   SourceLocation getBeginLoc() const { return Range.getBegin(); }
   SourceLocation getEndLoc() const { return Range.getEnd(); }
+  const ArrayRef<const OpenACCClause *> clauses() const { return Clauses; }
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alexey-bataev wrote:

```suggestion
  ArrayRef<const OpenACCClause *> clauses() const { return Clauses; }
```

https://github.com/llvm/llvm-project/pull/87675