Revisit batching of updates with `useOnyx`

[hannojg]

In this PR:

• Batch updates second try #315

We added support for batching updates, so that react only has to commit one big update, instead of updating every component separately. Back then there were only two subscription mechanisms:

• Onyx.connect
• withOnyx

Right now, we only batch updates for withOnyx. The reason for that is that in the NewDot code we have a lot of places that do Onyx.connect outside of react and immediately expect data. So we only wanted to batch withOnyx updates, as these were only used with react:

react-native-onyx/lib/OnyxUtils.ts

Lines 1004 to 1013 in c53826b

	function scheduleSubscriberUpdate<TKey extends OnyxKey>(
	key: TKey,
	value: OnyxValue<TKey>,
	previousValue: OnyxValue<TKey>,
	canUpdateSubscriber: (subscriber?: Mapping<OnyxKey>) => boolean = () => true,
	): Promise<void> {
	const promise = Promise.resolve().then(() => keyChanged(key, value, previousValue, canUpdateSubscriber, true, false));
	batchUpdates(() => keyChanged(key, value, previousValue, canUpdateSubscriber, false, true));
	return Promise.all([maybeFlushBatchUpdates(), promise]).then(() => undefined);
	}

Now we have useOnyx, which internally uses Onyx.connect, not withOnyx. So all components using useOnyx might not be batched.

I opened this issue because I want to look closer, if we need to enable a certain batching logic when using the useOnyx hook.

[hannojg]

Additionally, in fabric, react updates get batched automatically (if concurrent rendering is enabled) - so we might want to see if we can completely get rid of this manual batching mechanism.