New serverless pattern - cross account AMI monitoring solution

[naveen-amzn]

Issue #, if available:

Description of changes:
This solution will help customers to create auditing and monitoring solution for cross accounts shared AWS AMI. This will also alert customers when any de-registered AMI is still getting used in any AWS Service. This pattern will help customers to provide insights about AMI usage and reduce any production issue in case any de-registered AMI is referred in customers production account.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[jbesw]

Thanks for the submission but this is too complex for a pattern - please upload to a separate repo and submit as a Serverless Land repo at https://serverlessland.com/repos.