[llvm] ADT/Matrix: two-dimensional Container with View (PR #98893)

[Jakub Kuderski via llvm-commits]

kuhar wrote:

Say you define a function:
```c++
constexpr int add(int a, int b) { return a + b; }
```

this won't make any runtime call to `add` faster but it will allow you to write `static_assert(add(2 + 3) == 5);`

https://github.com/llvm/llvm-project/pull/98893