[llvm] [offload] Add opt-in `std::ostream` support to OffloadPrint.hpp (PR #222269)

[Łukasz Plewa via llvm-commits]

lplewa wrote:

> My main question is, why would we want to avoid the Support dependency when offload is an LLVM library?

SYCL headers for example - as far i remember @KseniyaTikhomirova wanted to use it there but due this dependency she couldn't. 

Also background is that we are working on integrating liboffload with our downstream SYCL benchmarks, so we can track and compare performance, to find some optimalisations, and this downstream benchmarks are out of this tree. 

https://github.com/llvm/llvm-project/pull/222269