* Recently CI runs started to hang randomly:
https://github.com/emilk/egui/actions/runs/17427449210/job/49477714447?pr=7359
This fixes the deadlock and adds the basic deadlock detection we also
added to Mutexes in #7468.
Also, interestingly, the more sophisticated deadlock detection (behind
the deadlock_detection feature) didn't catch this for some reason. I
wonder why it exists in the first place, when parking_lot also has built
in deadlock detection? It also seems to make tests slower, widget_tests
usually needs ~30s, with the deadlock detection removed its only ~12s.
fa4bee3bf7