Fixing Fabric Interop layer bug defaulting to UnstableLegacyViewManagerAutomaticComponentDescriptor irrespective of feature flag (facebook#50441)

Summary:
Pull Request resolved: facebook#50441

When useFabricInterop is disabled, deleting component descriptors in Component Registry is failing since  facebook#47321 removed the Fabric Interop check from the ComponentDescriptorRegistry.cpp which was added earlier in facebook#42294
Adding back the logic of Fallback component descriptor and error for the same.

Changelog:
[General][Fixed] Fixing Fabric Interop layer bug defaulting to UnstableLegacyViewManagerAutomaticComponentDescriptor irrespective of feature flags.

Reviewed By: javache

Differential Revision: D72266017

Author: arushikesarwani94

packages/react-native/ReactCommon/react/renderer/componentregistry/ComponentDescriptorRegistry.cpp

@@ -10,6 +10,7 @@
 #include "componentNameByReactViewName.h"
 
 #include <react/debug/react_native_assert.h>
+#include <react/featureflags/ReactNativeFeatureFlags.h>
 #include <react/renderer/componentregistry/ComponentDescriptorProviderRegistry.h>
 #include <react/renderer/components/legacyviewmanagerinterop/UnstableLegacyViewManagerAutomaticComponentDescriptor.h>
 #include <react/renderer/components/legacyviewmanagerinterop/UnstableLegacyViewManagerAutomaticShadowNode.h>
@@ -83,11 +84,21 @@ const ComponentDescriptor& ComponentDescriptorRegistry::at(
   }
 
   if (it == _registryByName.end()) {
-    auto componentDescriptor = std::make_shared<
-        const UnstableLegacyViewManagerAutomaticComponentDescriptor>(
-        parameters_, unifiedComponentName);
-    registerComponentDescriptor(componentDescriptor);
-    return *_registryByName.find(unifiedComponentName)->second;
+    if (ReactNativeFeatureFlags::useFabricInterop()) {
+      auto componentDescriptor = std::make_shared<
+          const UnstableLegacyViewManagerAutomaticComponentDescriptor>(
+          parameters_, unifiedComponentName);
+      registerComponentDescriptor(componentDescriptor);
+      return *_registryByName.find(unifiedComponentName)->second;
+    } else {
+      if (_fallbackComponentDescriptor == nullptr) {
+        throw std::invalid_argument(
+            ("Unable to find componentDescriptor for " + unifiedComponentName)
+                .c_str());
+      } else {
+        return *_fallbackComponentDescriptor.get();
+      }
+    }
   }
 
   return *it->second;