[clang] Patch series to reapply #118734 and substantially improve it (PR #120534)

[Chandler Carruth via cfe-commits]

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@@ -100,10 +244,17 @@ class Context {
 
   /// Return the identifier name for the specified builtin,
   /// e.g. "__builtin_abs".
-  llvm::StringRef getName(unsigned ID) const { return getRecord(ID).Name; }
+  std::string getName(unsigned ID) const;
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chandlerc wrote:

Eh, it was quite easy to search for all uses and audit them. Plus, Clang actually caught a bunch with warnings for me.

But sure, I've renamed it to `getFullName` since we might choose to surface the prefix distinction in the future.

https://github.com/llvm/llvm-project/pull/120534