Defer notifications while performing action

[ShirShintel]

• Add deferSubscriberNotifications Function that defers subscribers (and observables) notification until the end of some action. This is necessary when running a flow that creates intermediate states we don't want to react to.

• To handle the conflict between deferSubscriberNotifications and flush, add optional config to the flush function:

  • excecutionType: default- meaning flush would happen right after we stop deferring notifications. Flush when not deferring notifications stays the same.
  • excecutionType: scheduled- meaning flush would notify all without canceling render and requesting animation frame, regardless if notifications are currently being deferred.
  • excecutionType: immediate - meaning flush would happen immediately regardless if notifications are currently being deferred.

In general, the deferSubscriberNotifications solution is:

• deferSubscriberNotifications receives some action we would like to perform while deferring notifications.
• If notifications are already deferred, run action without doing anything else (to support nesting deferSubscriberNotifications)
• Set deferNotifications flag to true before running the action
• When calling notifyAll while deferNotifications is set to true, return without notifying
• Finally, set deferNotifications back to false, and flush\notify if someone tried to flush (not immediate) or notify while deferring notifications.

[shirlynwix]

Very nice!
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