[ECS] [Feature Suggestion]: Capacity Providers: Managed ASGs

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**Sharing a new Capacity Providers Feature Idea for Feedback from the Github Community.**

**Tell us about your request**
ECS should manage the lifecycle of the ASGs associated with the Capacity Providers. Including the AMI updates and Autoscaling.

**Which service(s) is this request for?**
ECS with EC2 Launch type

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
Users will get the Managed compute experience while retaining the observability of the underlying ASG instances. This will reduce the effort required to set up ECS clusters with the required compute Infrastructure and coupling the service and cluster Autoscaling. User can use Managed ASGs through ECS APIs and ECS will provision, manage Autoscaling policies, AMI updates and the lifecycle of the underlying ASGs powering their capacity providers. Since ECS provisions and controls the underlying Instances, ECS will be able to provide better draining and scaling workflows. Users also get he observability required for compliance reasons as the ASGs - Instances are in the customer accounts.

**What will the customer Experience look like?**
1. As part of the` create-capacity-providers` API customers can select the option of `--managed-ASG`
2. they can define additional configurations like instance type and Launch config - either within the capacity providers API or point to launch config (TBD)
3. ECS takes over the creation and managed of the AGS
4. Customers can see the ASG in their own accounts but it is largely read only , unless through ECS APIs
5. ECS provides the Automated AMI upgrade Management feature as part of this which allows customers to update their AMI using a 'Rolling Update' style refresh of the underlying EC2 Instances.

Please provide feedback with as much detail about your cases and feature request as a possible.

Start by reviewing the create-capacity-providers API request described in the issue and how ECS with the EC2 launch type currently relates to Auto Scaling Groups. The feature would be complete when ECS can provision and manage the ASG lifecycle, scaling policies, AMI updates, and instance draining while customers retain account-level observability.

Written by the indexing model from the issue text.