rusticl/event: another attempt of fixing stack overflows dropping long event dependency chains

I didn't like the solution and I think it even introduced a potential regressions involving releasing failed events and that causing dependents to run and succeed regardless.

Anyway, the new way is breaking dependency chains on drop making use of Arc::into_inner and some smartness to not always do it. I think in theory we can get really unlucky to run into stack overflows regardless, but let's see if we'll actually see any bugs on that.