[llvm] [memprof] Use CallStackRadixTreeBuilder in the V3 format (PR #94708)

[Teresa Johnson via llvm-commits]

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@@ -1028,6 +1036,10 @@ class CallStackRadixTreeBuilder {
   getCallStackPos() const {
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teresajohnson wrote:

Can we remove getCallStackPos and replace its users with takeCallStackPos? Looks like existing callers are all unit tests where we could do this.

https://github.com/llvm/llvm-project/pull/94708