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

[Aaron Ballman via cfe-commits]

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@@ -39,12 +39,13 @@ using namespace llvm;
 
 namespace {
 class DiagGroupParentMap {
-  RecordKeeper &Records;
-  std::map<const Record*, std::vector<Record*> > Mapping;
+  const RecordKeeper &Records;
+  std::map<const Record *, std::vector<const Record *>> Mapping;
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AaronBallman wrote:

Not for this PR, but maybe this should use a `MapVector`?

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