fix: RCTViewComponentView can become first responder only when enableImperativeFocus flag is enabled

[war-in]

Summary:

In RN 0.83, RCTViewComponentView.canBecomeFirstResponder was changed to unconditionally return YES as part of the enableImperativeFocus feature. This causes UIKit to promote parent views to first responder after navigation transitions complete (via _promoteSelfOrDescendantToFirstResponderIfNecessary), stealing focus from text inputs and triggering an immediate focus→blur cycle.

This fix gates canBecomeFirstResponder behind the enableImperativeFocus feature flag (which defaults to false), so views only become eligible for first responder when imperative focus is actually enabled.

Changelog:

[IOS] [FIXED] - Fixed RCTViewComponentView unconditionally returning YES from canBecomeFirstResponder, which caused focus to be stolen from text inputs after navigation transitions

Test Plan:

1. Create a screen with a TextInput that receives focus on mount (e.g. via autoFocus or a useEffect calling .focus()).
2. Navigate to that screen using a navigation library (e.g. React Navigation).
3. Verify the TextInput retains focus and the keyboard stays visible after the transition completes — previously the input would briefly gain then lose focus (focus→blur cycle).

[war-in]

cc @sbuggay as you were implementing the original PR. Please, let me know if that change makes sense 🙏