AWS::EC2::Instance - BlockDeviceMapping-Ebs-Throughput should support gp3 Throughput attribute

## 1. Title

#### AWS::EC2::Instance-BlockDeviceMapping-Ebs-Throughput

## 2. Scope of request

Please add support for Throughput on gp3-type EBS volumes in the BlockDeviceMapping.

## 3. Expected behavior

In Create, it should pass the Throughput parameter to the underlying CreateVolume call.
In Update, it should not require replacement when Throughput is changed.

## 4. Suggest specific test cases

Common use case: converting EC2 root volume from gp2 or another volume type to gp3 for extra iops/throughput on smaller disk sizes.
Common use case: referencing Throughput from a stack parameter, and changing Throughput.

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

- https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-ec2-blockdev-template.html

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

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

## 7. Any additional context (optional)

- #729
- #710
- #112

Review the linked CloudFormation EC2 BlockDeviceMapping documentation and related issues #729, #710, and #112 first. Verify that Create passes Throughput to CreateVolume and that Update changes Throughput without replacement, including parameter-driven changes.

Written by the indexing model from the issue text.