AWS::EC2::Instance support "replace root volume" with new AMI

### Name of the resource

AWS::EC2::Instance

### Resource name

_No response_

### Description

The new "replace root volume" with an AMI feature is not available in CFN
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/replace-root.html#replace-ami

This allows the root volume AMI to be replaced without replacing the instance.

Currently we use `BlockDeviceMappings` to specify an EBS volume as the instance root
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-ec2-blockdev-mapping.html
And we specify the AMI via `ImageId`
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-ec2-instance.html#cfn-ec2-instance-imageid

We would like to be able to update the `ImageId` without replacing the instance by having CFN perform a root volume replacement using an AMI as described in the article above.

So e.g. given an instance like this:
```json
"myEC2Instance": {
"Type": "AWS::EC2::Instance",
"Properties": {
"BlockDeviceMappings": [
{
"DeviceName": "/dev/sda1",
"Ebs": {
"VolumeSize": 20,
"VolumeType": "gp2"
}
}
],
"ImageId": "ami-XXX"
}
```
We would like to update `ImageId` and have this replace the root volume with the new AMI without replacing the instance.

### Other Details

_No response_

Start by reading the linked EC2 root-volume replacement documentation and the CloudFormation references for AWS::EC2::Instance, ImageId, and BlockDeviceMappings. The requested outcome is that changing ImageId replaces the root volume using the new AMI without replacing the instance; the issue does not name implementation files or tests.

Written by the indexing model from the issue text.