Stabilize AWS Cloud9 module

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### Overview:

AWS Cloud9 is an integrated development environment, or IDE.

The AWS Cloud9 IDE offers a rich code-editing experience with support for several programming languages and runtime debuggers, and a built-in terminal. It contains a collection of tools that you use to code, build, run, test, and debug software, and helps you release software to the cloud.

You access the AWS Cloud9 IDE through a web browser. You can configure the IDE to your preferences. You can switch color themes, bind shortcut keys, enable programming language-specific syntax coloring and code formatting, and more.

[AWS Docs](https://docs.aws.amazon.com/cloud9/latest/user-guide/welcome.html)

### Maturity: CloudFormation Resources Only

See the [AWS Construct Library Module Lifecycle doc](https://github.com/aws/aws-cdk-rfcs/blob/master/text/0107-construct-library-module-lifecycle.md) for more information about maturity levels.

### Implementation:

See the [CDK API Reference](https://docs.aws.amazon.com/cdk/api/latest/docs/aws-cloud9-readme.html) for more implementation details.

### Issue list: