feat(GlobalScheduler): implement deferred removal of schedulers

[Antamansid]

Race condition in scheduler iteration

The performUpdate() method iterates through scheduler arrays while scheduler callbacks can call removeScheduler(), which modifies the arrays in-place using splice(). This causes iteration to skip elements when a scheduler is removed during the loop:
Loop at index j=1, processing scheduler B
Scheduler B calls removeScheduler() for themself at index 1
Array shifts: [A,B,C,D] → [A,C,D], so C moves from index 2 to index 1
Loop increments to j=2, skipping scheduler C entirely
Fixed by implementing deferred removal - schedulers are marked for deletion during iteration and actually removed before the next update cycle.

[gravity-ui-bot]

Preview is ready.

[Antamansid]

I admit, I spent a lot of time trying to figure out why sometimes it doesn't work.
If you try to install console.log() in hitTest debounce, you will see that it is not deleted from the GlobalScheduler, but is spinning endlessly. Perhaps this is a problem due to StrictMode and the fact that when the Graph is recreated, GlobalScheduler is not recreated.
The current fix with a queue for deletion, if anything, does not solve the problem.

All in all, there is no need to equate to null, since during iteration there is a check for the presence of an element in the array.