[llvm] [CodeGen] LiveRegMatrix: Use allocator through a unique_ptr (PR #120556)

[Akshat Oke via llvm-commits]

optimisan wrote:

### Merge activity

* **Jan 1, 4:22 AM EST**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/120556).


https://github.com/llvm/llvm-project/pull/120556