Use notifyAll in IOTaskRunnable.kick (CodeQL java/notify-instead-of-notify-all)

[vharseko]

Summary

Resolves the java/notify-instead-of-notify-all alert in IOTaskRunnable.

kick() woke a blocked worker with notify():

synchronized void kick() {
    if (!_notified) {
        _notified = true;
        notify();
    }
}

Each IOTaskRunnable has exactly one background thread (created in start()),
and that thread is the only one that ever calls wait() on the monitor (in
run()), so notify() and notifyAll() are functionally equivalent today.
However, notify() is fragile — if any other thread ever waited on the same
monitor, it could wake the wrong one and leave the worker blocked.

Fix

Use notifyAll(). With a single waiter it wakes exactly the same thread (no
thundering herd), and the wait loop already re-checks its guards
(shouldStop() / _notified / recomputed wait time), so additional wake-ups are
handled correctly.

Testing

mvn -o -pl persistit/core compile — BUILD SUCCESS.