Delete dead RCTCxxBridgeDelegate protocol

Summary:
The C++ bridge delegate protocol has no implementers left: its only method served the removed `RCTCxxBridge`. Delete the header with its build entry, the stale forward declaration, and the unused imports.

Changelog:
[iOS][Removed] - Remove unused `RCTCxxBridgeDelegate` protocol

Differential Revision: D127294781

Author: christophpurrer

packages/react-native/Libraries/AppDelegate/RCTRootViewFactory.h

@@ -11,7 +11,6 @@
 #import <React/RCTUtils.h>
 #import "RCTJSRuntimeConfiguratorProtocol.h"
 
-@protocol RCTCxxBridgeDelegate;
 @protocol RCTComponentViewFactoryComponentProvider;
 @protocol RCTTurboModuleManagerDelegate;
 @protocol RCTHostDelegate;

packages/react-native/React/CxxBridge/RCTCxxBridgeDelegate.h

@@ -2574,10 +2574,6 @@ protocol RCTCustomRefreshControlProtocol {
   public @property (weak) UIScrollView* scrollView;
 }
 
-protocol RCTCxxBridgeDelegate : public RCTBridgeDelegate {
-  public virtual std::unique_ptr<facebook::react::JSExecutorFactory> jsExecutorFactoryForBridge:(RCTBridge* bridge);
-}
-
 protocol RCTDebuggingOverlayViewProtocol : public NSObject {
   public virtual void clearElementsHighlights();
   public virtual void highlightElements:(const NSArray* elements);

scripts/cxx-api/api-snapshots/ReactAppleDebugCxx.api

@@ -2636,10 +2636,6 @@ protocol RCTCustomRefreshControlProtocol {
   public @property (weak) UIScrollView* scrollView;
 }
 
-protocol RCTCxxBridgeDelegate : public RCTBridgeDelegate {
-  public virtual std::unique_ptr<facebook::react::JSExecutorFactory> jsExecutorFactoryForBridge:(RCTBridge* bridge);
-}
-
 protocol RCTDebuggingOverlayViewProtocol : public NSObject {
   public virtual void clearElementsHighlights();
   public virtual void highlightElements:(const NSArray* elements);

scripts/cxx-api/api-snapshots/ReactAppleFrameworksCxx.api

@@ -2567,10 +2567,6 @@ protocol RCTCustomRefreshControlProtocol {
   public @property (weak) UIScrollView* scrollView;
 }
 
-protocol RCTCxxBridgeDelegate : public RCTBridgeDelegate {
-  public virtual std::unique_ptr<facebook::react::JSExecutorFactory> jsExecutorFactoryForBridge:(RCTBridge* bridge);
-}
-
 protocol RCTDebuggingOverlayViewProtocol : public NSObject {
   public virtual void clearElementsHighlights();
   public virtual void highlightElements:(const NSArray* elements);

scripts/cxx-api/api-snapshots/ReactAppleNewarchCxx.api

@@ -2574,10 +2574,6 @@ protocol RCTCustomRefreshControlProtocol {
   public @property (weak) UIScrollView* scrollView;
 }
 
-protocol RCTCxxBridgeDelegate : public RCTBridgeDelegate {
-  public virtual std::unique_ptr<facebook::react::JSExecutorFactory> jsExecutorFactoryForBridge:(RCTBridge* bridge);
-}
-
 protocol RCTDebuggingOverlayViewProtocol : public NSObject {
   public virtual void clearElementsHighlights();
   public virtual void highlightElements:(const NSArray* elements);