[llvm] [Offload] Add `MAX_WORK_GROUP_SIZE` device info query (PR #143718)

[Ross Brunton via llvm-commits]

RossBrunton wrote:

@jhuber6 @callumfare The surrounding code for handling device information has changed a lot recently, so I think a lot of your concerns with this were fixed elsewhere. When you get a chance, can you take another look into this?

https://github.com/llvm/llvm-project/pull/143718