[d3d12] Rework signal handlers to dump debug info. Prevent rogue pointer access.#1076

manon-traverse merged 2 commits intollvm:mainllvm/offload-test-suite:mainfrom

Traverse-Research:render-backend-dx12-signal-handlerTraverse-Research/offload-test-suite:render-backend-dx12-signal-handlerCopy head branch name to clipboard