[clang-tools-extra] [clang-tidy][NFC] Refactor `modernize-use-trailing-return-type-check` check code and tests (PR #140759)

[Carlos Galvez via cfe-commits]

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@@ -113,7 +113,7 @@ struct UnqualNameVisitor : public RecursiveASTVisitor<UnqualNameVisitor> {
 };
 } // namespace
 
-constexpr llvm::StringLiteral Message =
+constexpr llvm::StringLiteral MessageFunction =
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carlosgalvezp wrote:

Nit: I think the name was clearer before. I read this as "the function that does something with the message". 

Maybe `ErrorMessage` would be more accurate?

https://github.com/llvm/llvm-project/pull/140759