feat: Add support for Modal on iOS when Fabric is enabled (#34487)

Summary:
While working on a fix for #29974 (I have a draft for that already (gabrieldonadel#16), just waiting for #34406 to get merged) I noticed that the `KeyboardAvoidingView` tests on RNTester on iOS were not working with Fabric enabled because the `ModalHostView` component was still not implemented. Upon some more investigation, I found this code suggestion from Milker90 (#33652 (comment)) that enables the Modal component on iOS when Fabric is enabled.

Closes #33652

## Changelog

[iOS] [Added] - Add support for Modal on iOS when Fabric is enabled

Pull Request resolved: #34487

Test Plan:
1. With Fabric enabled open the RNTester app and navigate to the Modal page
2. Test the `Modal` component through the sections changing props

https://user-images.githubusercontent.com/11707729/186289099-5223907d-b300-46bf-bfde-73259c29d544.mov

Reviewed By: christophpurrer

Differential Revision: D38981895

Pulled By: cipolleschi

fbshipit-source-id: cd493a8d2035900da2576323bc112e2565df4834

React/Fabric/Mounting/ComponentViews/RCTFabricComponentsPlugins.h

@@ -42,6 +42,7 @@ Class<RCTComponentViewProtocol> RCTTextInputCls(void) __attribute__((used));
 Class<RCTComponentViewProtocol> RCTInputAccessoryCls(void) __attribute__((used));
 Class<RCTComponentViewProtocol> RCTViewCls(void) __attribute__((used));
 Class<RCTComponentViewProtocol> RCTImageCls(void) __attribute__((used));
+Class<RCTComponentViewProtocol> RCTModalHostViewCls(void) __attribute__((used));
 
 #ifdef __cplusplus
 }

React/Fabric/Mounting/ComponentViews/RCTFabricComponentsPlugins.mm

@@ -30,6 +30,7 @@
     {"InputAccessoryView", RCTInputAccessoryCls},
     {"View", RCTViewCls},
     {"Image", RCTImageCls},
+    {"ModalHostView", RCTModalHostViewCls},
   };
 
   auto p = sFabricComponentsClassMap.find(name);