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

[Aiden Grossman via cfe-commits]

boomanaiden154 wrote:

I believe this is ready to go now. All the tests have been converted to lit-style tests and everything has been wired up into a `check-mlgo-utils` CMake target.

I talked with Mircea about the absl dependency. It's not in the tests anymore and the plan is to refactor in a subsequent commit the rest of the utilities that use absl to the generic python versions. For now the tests have been gated to actually having `absl` installed.

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