refactor(mobile): cleanup iOS image loading pipeline (#27672)

* refactor: replace DispatchQueue + DispatchSemaphore with OperationQueue for image processing

* implement RequestRegistry and UnfairLock for managing cancellable requests

* implement requests registry for local and remote image processing

* remove Cancellable protocol and cancel method from request registry

* refactor: introduce ImageRequest base class with unified cancellation and finish helpers

* refactor: add get method to RequestRegistry and streamline request removal in image processing

* add guard to cancel to prevent double onCancel calls

* fix duplicate code merge issue

* refactor(ios): enhance finish method to return callback status

* remove unfitting methods form ImageRequest.swift and fix memory issue

* revert bad merge

* refactor(ios): resolve cancellation issues

* refactor(ios): streamline image request completion handling

* add return statements

* refactor(ios): simplify image request cancellation and registry handling

---------

Co-authored-by: Alex <alex.tran1502@gmail.com>

mobile/ios/Runner/Images/ImageRequest.swift

@@ -1,5 +1,32 @@
 import Foundation
 
+class ImageRequest: @unchecked Sendable {
+  private struct State: Sendable {
+    var isCancelled = false
+  }
+
+  let completion: @Sendable (Result<[String: Int64]?, any Error>) -> Void
+  private let state: Mutex<State>
+
+  var isCancelled: Bool {
+    get {
+      state.withLock { $0.isCancelled }
+    }
+    set {
+      state.withLock { $0.isCancelled = newValue }
+    }
+  }
+
+  init(completion: @escaping @Sendable (Result<[String: Int64]?, any Error>) -> Void) {
+    self.state = Mutex(State())
+    self.completion = completion
+  }
+
+  func cancel() {
+    isCancelled = true
+  }
+}
+
 struct RequestRegistry<T: AnyObject & Sendable>: ~Copyable, Sendable {
   private let requests = Mutex<[Int64: T]>([:])