[llvm] [memprof] Add Version2 of the indexed MemProf format (PR #89100)

[Snehasish Kumar via llvm-commits]

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@@ -200,6 +200,9 @@ class InstrProfWriter {
   // Internal interface for testing purpose only.
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snehasish wrote:

Update the comment to indicate that all the methods are testing only?

https://github.com/llvm/llvm-project/pull/89100