[llvm] [offload] Change olLaunchKernel to accept argument arrays (PR #173263)

[Joseph Huber via llvm-commits]

jhuber6 wrote:

Now that I think about it, we might even be able to make an argument for removing the `size` argument. Kernels should know the size of the buffer they need, it's not like anything works if the size is incorrect. Launching kernels could then be made more convenient with a simple helper like
```c++
auto args = make_args(a, b, c);
launch_kernel(args.data(), ...);
```

But we can save these arguments for later

https://github.com/llvm/llvm-project/pull/173263