[llvm] [memprof] Update comments for writeMemProf and its helpers (PR #92446)

[Teresa Johnson via llvm-commits]

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@@ -521,6 +532,18 @@ static Error writeMemProfV0(ProfOStream &OS,
   return Error::success();
 }
 
+// Write out MemProf Version1 as follows:
+// uint64_t Version
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teresajohnson wrote:

consider adding something like "NEW in v1" or something here and similar for the new in v2 fields there.

https://github.com/llvm/llvm-project/pull/92446