[iOS] Fix TextInputAction.continueAction sends wrong action to framework (flutter/engine#42615)

## Description

This PR fixes an issue related to text input plugin, on IOS, sending a wrong action string to the engine for `FlutterTextInputActionContinue`.

## Related Issue

Fixes https://github.com/flutter/flutter/issues/126922

## Tests

Adds 1 test.

engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterEngine.mm

@@ -1009,7 +1009,7 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
       actionString = @"TextInputAction.next";
       break;
     case FlutterTextInputActionContinue:
-      actionString = @"TextInputAction.continue";
+      actionString = @"TextInputAction.continueAction";
       break;
     case FlutterTextInputActionJoin:
       actionString = @"TextInputAction.join";

engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterEngine_Test.h

@@ -4,6 +4,7 @@
 
 #import "flutter/shell/common/shell.h"
 #import "flutter/shell/platform/darwin/ios/framework/Headers/FlutterEngine.h"
+#import "flutter/shell/platform/darwin/ios/framework/Source/FlutterTextInputDelegate.h"
 #import "flutter/shell/platform/darwin/ios/rendering_api_selection.h"
 #include "flutter/shell/platform/embedder/embedder.h"
 
@@ -31,4 +32,7 @@ class ThreadHost;
                        entrypointArgs:(/*nullable*/ NSArray<NSString*>*)entrypointArgs;
 - (const flutter::ThreadHost&)threadHost;
 - (void)updateDisplays;
+- (void)flutterTextInputView:(FlutterTextInputView*)textInputView
+               performAction:(FlutterTextInputAction)action
+                  withClient:(int)client;
 @end

engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterTextInputPluginTest.mm

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#import "flutter/shell/platform/darwin/ios/framework/Source/FlutterBinaryMessengerRelay.h"
+#import "flutter/shell/platform/darwin/ios/framework/Source/FlutterEngine_Test.h"
 #import "flutter/shell/platform/darwin/ios/framework/Source/FlutterTextInputPlugin.h"
 
 #import <OCMock/OCMock.h>
@@ -308,7 +310,7 @@ FLUTTER_ASSERT_ARC
                                 withClient:0]);
 }
 
-- (void)testIngoresSelectionChangeIfSelectionIsDisabled {
+- (void)testIgnoresSelectionChangeIfSelectionIsDisabled {
   FlutterTextInputView* inputView = [[FlutterTextInputView alloc] initWithOwner:textInputPlugin];
   __block int updateCount = 0;
   OCMStub([engine flutterTextInputView:inputView updateEditingClient:0 withState:[OCMArg isNotNil]])
@@ -678,6 +680,27 @@ FLUTTER_ASSERT_ARC
   XCTAssertFalse(inputView.isSecureTextEntry);
 }
 
+- (void)testInputActionContinueAction {
+  id mockBinaryMessenger = OCMClassMock([FlutterBinaryMessengerRelay class]);
+  FlutterEngine* testEngine = [[FlutterEngine alloc] init];
+  [testEngine setBinaryMessenger:mockBinaryMessenger];
+  [testEngine runWithEntrypoint:FlutterDefaultDartEntrypoint initialRoute:@"test"];
+
+  FlutterTextInputPlugin* inputPlugin =
+      [[FlutterTextInputPlugin alloc] initWithDelegate:(id<FlutterTextInputDelegate>)testEngine];
+  FlutterTextInputView* inputView = [[FlutterTextInputView alloc] initWithOwner:inputPlugin];
+
+  [testEngine flutterTextInputView:inputView
+                     performAction:FlutterTextInputActionContinue
+                        withClient:123];
+
+  FlutterMethodCall* methodCall =
+      [FlutterMethodCall methodCallWithMethodName:@"TextInputClient.performAction"
+                                        arguments:@[ @(123), @"TextInputAction.continueAction" ]];
+  NSData* encodedMethodCall = [[FlutterJSONMethodCodec sharedInstance] encodeMethodCall:methodCall];
+  OCMVerify([mockBinaryMessenger sendOnChannel:@"flutter/textinput" message:encodedMethodCall]);
+}
+
 #pragma mark - TextEditingDelta tests
 - (void)testTextEditingDeltasAreGeneratedOnTextInput {
   FlutterTextInputView* inputView = [[FlutterTextInputView alloc] initWithOwner:textInputPlugin];