Dropping JoinHandle does not cause deallocation

[senyosimpson]

When a task starts, it has a reference count of 2. If the JoinHandle is dropped, we can only run a task once before it gets deallocated (since a Task will cause a ref decrement on yield/completion). This is not correct. It should complete since it was not explicitly cancelled.

[senyosimpson]

Turns out this doesn't work in practice (in my executor). Reason being is that whenever a waker is registered, it is cloned. So we always end up with enough ref counts to keep a task valid. This may not always be true however but right now it is and therefore I can ignore this problem.

[senyosimpson]

yerrr this is gibberish to me now lmao