[fabric] Make text input first responder through the window instance

Summary:
Fix AppKit exception throws when focusing text inputs by calling becomeFirstResponder directly on the backing text input view.

Making a view first responder has to happen through the window using makeFirstResponder.

Test Plan:
- Run Zeratul with Fabric
- Focus the search text input above the message threads
- Click inside the active message thread to trigger the auto-focus of the composer
- The composer gets focus without AppKit throwing an exception.

 https://pxl.cl/3dVMx

Reviewers: shawndempsey, #rn-desktop

Reviewed By: shawndempsey

Differential Revision: https://phabricator.intern.facebook.com/D48696690

packages/react-native/React/Fabric/Mounting/ComponentViews/TextInput/RCTTextInputComponentView.mm

@@ -528,7 +528,14 @@ - (void)handleCommand:(const NSString *)commandName args:(const NSArray *)args
 
 - (void)focus
 {
+#if !TARGET_OS_OSX // [macOS]
   [_backedTextInputView becomeFirstResponder];
+#else // [macOS
+  NSWindow *window = _backedTextInputView.window;
+  if (window) {
+    [window makeFirstResponder:_backedTextInputView];
+  }
+#endif // macOS]
 
   const auto &props = static_cast<const TextInputProps &>(*_props);