feat(mobile): add support for encoded image requests in local/remote image APIs (#26584)

* feat(mobile): add support for encoded image requests in local and remote image APIs

* fix(mobile): handle memory cleanup for cancelled image requests

* refactor(mobile): simplify memory management and response handling for encoded image requests

* fix(mobile): correct formatting in cancellation check for image requests

* Apply suggestion from @mertalev

Co-authored-by: Mert <101130780+mertalev@users.noreply.github.com>

* refactor(mobile): rename 'encoded' parameter to 'preferEncoded' for clarity in image request APIs

* fix(mobile): ensure proper resource cleanup for cancelled image requests

* refactor(mobile): streamline codec handling by removing unnecessary descriptor disposal in loadCodec request

---------

Co-authored-by: Mert <101130780+mertalev@users.noreply.github.com>

mobile/pigeon/local_image_api.dart

@@ -21,6 +21,7 @@ abstract class LocalImageApi {
     required int width,
     required int height,
     required bool isVideo,
+    required bool preferEncoded,
   });
 
   void cancelRequest(int requestId);

mobile/pigeon/remote_image_api.dart

@@ -19,6 +19,7 @@ abstract class RemoteImageApi {
     String url, {
     required Map<String, String> headers,
     required int requestId,
+    required bool preferEncoded,
   });
 
   void cancelRequest(int requestId);