Repository: flutter
Issue: [Multiple Flutter]MissingPluginException: No implementation found for method incrementCount on channel 
Labels: platform-android,engine,a: existing-apps,P2,team-android,triaged-android

<!-- Thank you for using Flutter!

     If you are looking for support, please check out our documentation
     or consider asking a question on Stack Overflow:
      * https://flutter.dev/
      * https://api.flutter.dev/
      * https://stackoverflow.com/questions/tagged/flutter?sort=frequent

     If you have found a bug or if our documentation doesn't have an answer
     to what you're looking for, then fill out the template below. Please read
     our guide to filing a bug first: https://flutter.dev/docs/resources/bug-reports
-->

## Steps to Reproduce

<!-- Please include full steps to reproduce so that we can reproduce the problem. -->

1. FlutterEngine is  2.8.1 Prepare FlutterFragment A and B, 
2. each fragmnet has an engine created with the flutterEngineGroup
2. each engine will registers all plug-ins channel,
2. however, an error will be reported every time when i used channel in fragment B 。exception content： “Unhandled Exception: MissingPluginException(No implementation found for method xxxx)”
3. ... do not use flutterEngineGroup create engine,it's ok.
4. The official demo had the same problem when click add buttion For example the following pic，code address：[git@github.com:flutter/samples.git](https://github.com/flutter/samples/tree/master/add_to_app/multiple_flutters)

<img src="https://user-images.githubusercontent.com/31503964/151525446-c297186d-274b-47c2-83d5-ce65233b257b.png" width ="300">

Expected results:
we can use channel normally 

Actual results:
an error will be reported every time when i used channel in fragment A or B ，exception content： “Unhandled Exception: MissingPluginException(No implementation found for method xxxx)”


flutter doctor -v

```
Flutter (Channel stable, 2.8.1, on Mac OS X 10.15.5 19F101 darwin-x64,
    locale zh-Hans-CN)
    • Flutter version 2.8.1 at /Users/jonyzhang/fvm/versions/2.8.1
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 77d935af4d (6 weeks ago), 2021-12-16 08:37:33 -0800
    • Engine revision 890a5fca2e
    • Dart version 2.15.1
    • Pub download mirror https://pub.flutter-io.cn

[!] Android toolchain - develop for Android devices (Android SDK version
    32.0.0)
    • Android SDK at /Users/jonyzhang/Library/Android/sdk
    ✗ cmdline-tools component is missing
      Run `path/to/sdkmanager --install "cmdline-tools;latest"`
      See https://developer.android.com/studio/command-line for more details.
    ✗ Android license status unknown.
      Run `flutter doctor --android-licenses` to accept the SDK licenses.
      See https://flutter.dev/docs/get-started/install/macos#android-setup for
      more details.

[!] Xcode - develop for iOS and macOS (Xcode 12.2)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    ! Flutter recommends a minimum Xcode version of 13.0.0.
      Download the latest version or update via the Mac App Store.
    ✗ CocoaPods not installed.
        CocoaPods is used to retrieve the iOS and macOS platform side's plugin
        code that responds to your plugin usage on the Dart side.
        Without CocoaPods, plugins will not work on iOS or macOS.
        For more info, see https://flutter.dev/platform-plugins
      To install see
      https://guides.cocoapods.org/using/getting-started.html#installation for
      instructions.

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 3.5)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build
      1.8.0_202-release-1483-b49-5587405)
```
<!--
      Consider also attaching screenshots and/or videos to better
      illustrate the issue.

      You can upload them directly on GitHub.
      Beware that video file size is limited to 10MB.
-->