[llvm] [Offload] Add olGetKernelMaxGroupSize (PR #142950)

[Joseph Huber via llvm-commits]

https://github.com/jhuber6 commented:

I know we've probably covered this before but I need to reorient myself here. But what was the issue with something like this again?

```c++
olGetSymbolInfo(symbol_t symbol, attribute attr, void *data);

uint32_t size;
symbol_t sym = olGetSymbol("foo");
olGetSymbolinfo(sym, OL_SYMBOL_INFO_MAX_GROUP_SIZE, &size);
```

https://github.com/llvm/llvm-project/pull/142950