AWS::EC2::Instance -BlockDeviceMapping-Ebs should allow volume changes without replacing the instance

## 1. AWS::EC2::Instance -BlockDeviceMapping-Ebs should allow volume changes without replacing the instance

## 2. Scope of request
It should be possible to change EBS volume attributes (such as `VolumeSize` or `VolumeType`) for volumes specified in the `BlockDeviceMappings` property of an `AWS::EC2::Instance` resource without re-creating the instance. For example, being able to re-size (via CloudFormation) the root volume of an instance.

This is currently possible via the API/Console, but not via CloudFormation.

## 3. Expected behavior

On modification of (at least the `VolumeSize` and `VolumeType` properties) the `AWS::EC2::Instance` resource should not be re-created, just the underlying volume properties modified.

## 4. Suggest specific test cases

#### Common use case: pass `VolumeSize` and`VolumeType` parameters as a string, or as a !Ref

## 5. Helpful Links to speed up research and evaluation

https://docs.aws.amazon.com/AWSEC2/latest/APIReference/API_ModifyVolume.html

## 6. Category (required) - Will help with tagging and be easier to find by other users to +1

1. Compute (EC2, ECS, EKS, Lambda...)