focus/blur event emission (#53826)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/53826

Wires up focus/blur events to the base event emitter, gated by enabledImperativeFocus feature flag.

https://docs.google.com/document/d/1L4ViBnXq5hw858VoecZPmJE2llOB97Tjs2VtJ7RHlNI/edit?tab=t.0

Changelog: [Internal]

Reviewed By: rozele

Differential Revision: D82146275

fbshipit-source-id: 4b7bb1336f74bb0de2d7ecf0737dd63067bd558f

packages/react-native/ReactCommon/react/renderer/components/view/BaseViewEventEmitter.cpp

@@ -112,4 +112,13 @@ void BaseViewEventEmitter::onLayout(const LayoutMetrics& layoutMetrics) const {
   });
 }
 
+#pragma mark - Focus
+void BaseViewEventEmitter::onFocus() const {
+  dispatchEvent("focus");
+}
+
+void BaseViewEventEmitter::onBlur() const {
+  dispatchEvent("blur");
+}
+
 } // namespace facebook::react

packages/react-native/ReactCommon/react/renderer/components/view/BaseViewEventEmitter.h

@@ -32,6 +32,10 @@ class BaseViewEventEmitter : public TouchEventEmitter {
 
   void onLayout(const LayoutMetrics& layoutMetrics) const;
 
+#pragma mark - Focus
+  void onFocus() const;
+  void onBlur() const;
+
  private:
   /*
    * Contains the most recent `frame` and a `mutex` protecting access to it.