[clang] [clangl[TableGen] Change Diagnostic Emitter to use const RecordKeeper (PR #108209)

[Aaron Ballman via cfe-commits]

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@@ -68,7 +69,8 @@ getCategoryFromDiagGroup(const Record *Group,
 
   // The diag group may the subgroup of one or more other diagnostic groups,
   // check these for a category as well.
-  const std::vector<Record*> &Parents = DiagGroupParents.getParents(Group);
+  const std::vector<const Record *> &Parents =
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AaronBallman wrote:

Should we change this to use an `ArrayRef`? (Same for the `getParents()` API?)

https://github.com/llvm/llvm-project/pull/108209