[Web] Attach handlers in the handlerTags order instead of creation order

[j-piasecki]

Description

#4179 changed how gestures are attached to the host detector. This resulted in handlers being attached in the creation order instead of the order in handlerTags like before. This didn't have an impact on Android/iOS, but the web turned out to be specifically sensitive to this.

While the sensitivity to the attach order needs to be investigated, this PR restores the previous behavior by batching the response to the gesture-ready callbacks and attaching all prepared handlers based on the handlerTags order.

Test plan

Test the web example app, especially Nested Pressables.

[Copilot]

Pull request overview

Restores deterministic gesture-handler attachment ordering on web by batching NodeManager.observeHandler “ready” callbacks into a single microtask flush, so handlers are attached in handlerTags (subscription) order rather than React effect creation order (regression introduced in #4179).

Changes:

• Batch handler-ready observer callbacks via a microtask and attach all ready handlers in one flush.
• Refactor attach flow to attach/update top-level and virtual handlers from stored subscriptions.
• Simplify syncSubscriptions API and observer callback wiring to route through the batched flush.

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