[llvm] ConstraintSystem: replace data structure with Matrix (PR #98895)

[Jakub Kuderski via llvm-commits]

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+//===- Matrix.h - Two-dimensional Container with View -----------*- C++ -*-===//
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kuhar wrote:

Would it be possible to first have this code live somewhere local to `ConstraintSystem` and once it matures / gains more usage, promote it to ADT?

https://github.com/llvm/llvm-project/pull/98895