[clang-tools-extra] [llvm] [MLGO] Upstream the corpus extraction tooling (PR #72319)

[Aiden Grossman via cfe-commits]

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+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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boomanaiden154 wrote:

Or what's probably better for structuring is we can do `mlgo/mlgo/corpus` and then the package would be accessed as `mlgo.corpus` while still keeping everything together if we want to add more in the future. I'll switch to that for now.

https://github.com/llvm/llvm-project/pull/72319