Bring back SharedImageManager = std::shared_ptr<ImageManager> alias to allow gradual API migration (#52888)

Summary:
Pull Request resolved: #52888

This brings back the type erased in  #52747 to fix build breaks in consuming libraries as: `react-native-svg`

https://github.com/facebook/react-native/actions/runs/16560124464/job/46828273956?fbclid=IwY2xjawL0f1dleHRuA2FlbQIxMQBicmlkETFXVnFJUkhXMDNkSlJhY1c1AR6vMc_wUFxgfUN-JsCFMzl4L2V2JaSfX37gKIoUu8U9WGGmb0JBG1LNl0Ogjg_aem_aM4XSISUjhqE7S8_QA2KfA

Changelog: [General][Fixed] Bring back SharedImageManager = std::shared_ptr<ImageManager> alias

Reviewed By: cipolleschi

Differential Revision: D79097253

fbshipit-source-id: afec0b4dd706fac91ba296d2bf2a50fb27200597

Author: christophpurrer

packages/react-native/ReactCommon/react/renderer/imagemanager/ImageManager.h

@@ -7,6 +7,8 @@
 
 #pragma once
 
+#include <memory>
+
 #include <react/renderer/core/ReactPrimitives.h>
 #include <react/renderer/imagemanager/ImageRequest.h>
 #include <react/renderer/imagemanager/ImageRequestParams.h>
@@ -15,6 +17,12 @@
 
 namespace facebook::react {
 
+class ImageManager;
+
+using SharedImageManager
+    [[deprecated("Use std::shared_ptr<ImageManager> instead.")]] =
+        std::shared_ptr<ImageManager>;
+
 /*
  * Cross platform facade for image management (e.g. iOS-specific
  * RCTImageManager)