udev doesn't work in sandboxes, notably the new Steam container runtime
as found notably on the Steam Deck, and in Flatpak/Snap packages.
Like SDL does, when we detect such a containerized environment, we fall
back to parsing `/dev/input` directly.
See smcv's comments in #76879 for details.
Fixes#76879.
(cherry picked from commit 788cb74cc676627b6c9b7e29a47200141cca92ff)