[clang] [analyzer][NFC] Document and centralize the CallEvent argument/parameter index mapping (PR #221252)

[Benedek Kaibas via cfe-commits]

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@@ -429,6 +432,9 @@ class CallEvent {
   /// if we are supposed to construct an argument directly, we may still
   /// not do that because we don't know how (i.e., construction context is
   /// unavailable in the CFG or not supported by the analyzer).
+  ///
+  /// \param Index index of the argument as understood by the AST.
+  /// See getASTArgumentIndex().
   bool isArgumentConstructedDirectly(unsigned Index) const {
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benedekaibas wrote:

Applied changes here: [0e7a71b](https://github.com/llvm/llvm-project/pull/221252/commits/0e7a71bc3d7705c088faad6ac46481a1048077d5)

https://github.com/llvm/llvm-project/pull/221252