Enhancement to CDK/Linux/hello-world example

[hu-jin-aws]

This PR is an enhancement to the code under CDK/Linux/hello-world to support user specifying AWS Management Components in the EC2 Image Builder Pipeline configurations. It also included some general cleanup. Below are the detailed list of the changes:

• Update formatting and misc cosmetics fix
• Support multiple components in one recipe
• Support AWS managed components
• Support specifying path to single spec file
• Remove unused S3 bucket
• A few other misc fixes
• Update README

[hu-jin-aws]

@ynyany As you are the original author of this part of the code, can you please review?

[hu-jin-aws]

@austoonz To keep the history clean I have rebased two new commits of addressing review comments into the original commit, therefore it might be a little hard to see the changes when you review. Apologies for that.