[Support] On Windows 11 and Windows Server 2022, fix an affinity mask issue on...

[Support] On Windows 11 and Windows Server 2022, fix an affinity mask issue on large core count machines

Before Windows 11 and Windows Server 2022, only one 'processor group' is assigned by default to a starting process, then the program is responsible for dispatching its own threads on more 'processor groups'. That is what 8404aeb5 was doing, allowing LLVM tools to automatically use all hardware threads in the machine.

After Windows 11 and Windows Server 2022, the OS takes care of that. This has an adverse effect reported in #56618 which is that using `GetProcessAffinityMask()` API in some edge cases seems buggy now. That API is used to detect if an affinity mask was set, and adjust accordingly the available threads for a ThreadPool.

With this patch, on one hand, we let the OS dispatch threads on all 'processor groups', but only for Windows 11 & Windows Server 2022 and after. We retain the old behavior for older OS versions. On the other hand, a workaround was added to mitigate the `GetProcessAffinityMask()` issue described above (see Threading.inc, L226).

Differential Revision: https://reviews.llvm.org/D138747