Migrate the code related to app-framewrok to a new code repository.

[FromLiQg]

Hello to all developers who use WAMR. We decided to migrate the code related to app-framework to an independent repository wamr-app-framework under bytecodealliance.
Before we go into the details, we apologize for any inconvenience this may cause to developers using WAMR. If you are using the app-framework related code for your business, this action may have an impact on your operations.

There are two reasons why we decided to separate the wamr-app-framework from the wamr:

1. The current directory structure of wamr is quite complex, which makes document management burdensome and brings additional learning costs to some developers using WAMR.
2. This decision was made based during the WAMR TSC meeting after discussions and we will migrate the code related to the app-framework to an independent repository.
   What will be migrated out:

• core/app-framework
• core/app-mgr
• assembly-script
• samples/gui
• samples/littlevgl
• samples/simple
• test-tools/IoT-APP-Store-Demo
• test-tools/component-test
• test-tools/host-tool
• part of wamr-sdk related to app-framework

The meeting notes:
https://github.com/bytecodealliance/wasm-micro-runtime/wiki/TSC-meeting-notes.

The new repository:
https://github.com/bytecodealliance/wamr-app-framework

The related PRs:
bytecodealliance/wamr-app-framework#1
#2305