[llvm] [ctx_prof] Extend `WorkloadImportsManager` to use the contextual profile (PR #98682)

[Mircea Trofin via llvm-commits]

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@@ -174,6 +174,10 @@ static cl::opt<std::string> WorkloadDefinitions(
              "}"),
     cl::Hidden);
 
+static cl::opt<std::string>
+    ContextualProfile("thinlto-pgo-ctx-prof",
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mtrofin wrote:

We don't currently have a textual representation of the contextual profile, and the import manager is internal to this file, meaning we can't write a unittest. I'd do either, though, if the new functionality was more involved, but it's really just taking data from the ctx profile reader - which is tested - and filling a set with it.

I refactored a bit more to leave the specific code to a minimum.

https://github.com/llvm/llvm-project/pull/98682