EventTarget-based event dispatching (#56427)

[rubennorte]

Summary:

Changelog: [internal]

Context

React Native's event system currently dispatches events through a legacy
plugin-based system. This change sets up an experiment to migrate to
the W3C EventTarget API (addEventListener/removeEventListener/dispatchEvent),
which enables imperative event handling on refs and aligns with web standards.

The experiment is gated behind the enableNativeEventTargetEventDispatching
feature flag (defaults to off).

Changes

• Add EVENT_TARGET_GET_DECLARATIVE_LISTENER_KEY hook to EventTarget,
  allowing subclasses to provide prop-based listeners at dispatch time.
  In invoke(), the prop listener is prepended to the addEventListener
  listeners and processed through the same loop (no duplication).
• ReactNativeElement overrides this hook to look up handlers from
  canonical.currentProps using a reverse mapping from event names
  to prop names (built lazily from the view config in
  EventNameToPropName.js).
• Add getCurrentProps helper in NodeInternals.js to encapsulate
  private React API access.
• Conditionally extend ReadOnlyNode from EventTarget when the flag is
  enabled, making addEventListener/removeEventListener/dispatchEvent
  available on element refs.
• Export setEventInitTimeStamp and dispatchTrustedEvent from
  ReactNativePrivateInterface for use by the React renderer.
• Set up global RN$isNativeEventTargetEventDispatchingEnabled function
  for the React renderer to check the flag value.

Gated until the OSS renderer has been synced to OSS:

• Add integration tests for event dispatching (prop handlers,
  addEventListener, ordering, capture/bubble phases, timestamps) and
  responder system (grant, release, transfer, negotiation, capture).
• Add event dispatching benchmark.

Differential Revision: D100462547

[meta-codesync]

@rubennorte has exported this pull request. If you are a Meta employee, you can view the originating Diff in D100462547.