[ECS] [request]: Adding CloudFormation helper scripts (aws-cfn-bootstrap) to ECS-optimized AMI by default

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**Tell us about your request**
I would like to add a request regarding integrate and preinstall CloudFormation helper scripts for Amazon ECS-optimized AMIs.

**Which service(s) is this request for?**
ECS

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**

The Amazon Linux 2 ECS-optimized AMI doesn't include CloudFormation helper scripts by default, I was expecting the CloudFormation helper scripts should be preinstalled on Amazon Linux AMI images [1], but it is not applicable when I tried to use latest ECS AMI. I can see it doesn't include these scripts in `/opt/aws/bin ` and I have to install these scripts manually:

- AMI ID: `ami-0cce120e74c5100d4 `
- AMI: `amzn2-ami-ecs-hvm-2.0.20210504-x86_64-ebs`
- Region: `us-east-1`

```
lrwxrwxrwx 1 root root 32 May 8 02:29 cfn-hup -> ../apitools/cfn-init/bin/cfn-hup
lrwxrwxrwx 1 root root 33 May 8 02:29 cfn-init -> ../apitools/cfn-init/bin/cfn-init
lrwxrwxrwx 1 root root 35 May 8 02:29 cfn-signal -> ../apitools/cfn-init/bin/cfn-signal
...
```

It would be great if can include these common scripts by integrating the `aws-cfn-bootstrap` package, so I can use it to install software and start services on my ECS Container instances as part of workflow in my CloudFormation stack when provisioning my instances in private subnet.

**Are you currently working around this issue?**

Install the package manually [2]:

```bash
sudo yum install -y aws-cfn-bootstrap
```

[1] CloudFormation helper scripts reference - Amazon Linux AMI images - https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/cfn-helper-scripts-reference.html#cfn-helper-scripts-reference-amazon-amis
[2] CloudFormation helper scripts reference - Using the latest version - https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/cfn-helper-scripts-reference.html#cfn-helper-scripts-reference-latest-version

Start with the ECS-optimized AMI build configuration and verify the reported Amazon Linux 2 AMI state under /opt/aws/bin. Use the documented aws-cfn-bootstrap installation command as the baseline, then confirm that the helper scripts are present by default in the resulting AMI and remain usable for CloudFormation provisioning.

Written by the indexing model from the issue text.