Remove unused UIManager binding from React private interface (#58399) - #58399

@cortinico cortinico left a comment

Differential Revision: D119490598

Summary:
Remove the isOSS conditionals that were skipping Fantom renderer tests in OSS environments. Now that the React Native renderers have been upgraded and the code is compatible in OSS, these tests can run in both internal and OSS environments.
Changes:
- ResponderEventTarget-itest.js: Removed isOSS check that skipped the entire Responder System test suite
- EventTargetDispatching-itest.js: Removed isOSS check that skipped the entire EventTarget-based Event Dispatching test suite
- EventDispatching-benchmark-itest.js: Removed if (isOSS) block that provided a dummy test instead of the benchmark suite
- EventDispatching-itest.js: Removed if (!isOSS) condition guarding three tests for native event timeStamp and global event dispatching
Changelog: [Internal]
Differential Revision: D107675643

Summary:
The renderer can dispatch events either through the legacy plugin-based system or through the W3C EventTarget API (addEventListener/dispatchEvent), gated behind the enableNativeEventTargetEventDispatching feature flag. Enabling it by default was previously blocked on the renderer, which did not carry the necessary changes until React 19.3.0. That sync has now landed, so flip the flag's default value to true and drop the TODO that tracked the blocker.
Fully removing the flag and the legacy dispatch path is left for a follow-up.
Changelog:
[General][Changed] - Dispatch events through the EventTarget API by default
Differential Revision: D119495069

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Summary:
Pull Request resolved: react#58399
After Paper was cleaned up from React in react/react#36285 this property is no longer used in React and can be removed from the interface.
Changelog: [internal]
Reviewed By: cortinico
Differential Revision: D119166138