Feature Request: Add support for EC2 SnapShots tiering

Hello, It will be great if you can add the support for the following API calls regarding Tiering management of EC2 SnapShots: - [describe_snapshot_tier_status](https://docs.aws.amazon.com/boto3/latest/reference/services/ec2/client/describe_snapshot_tier_status.html) - [modify_snapshot_tier](https://docs.aws.amazon.com/boto3/latest/reference/services/ec2/client/modify_snapshot_tier.html) - [restore_snapshot_tier](https://docs.aws.amazon.com/boto3/latest/reference/services/ec2/client/restore_snapshot_tier.html) And filtering on [EC2.ServiceResource.snapshots.filter](https://docs.aws.amazon.com/boto3/latest/reference/services/ec2/service-resource/snapshots.html#filter) too for key 'storage-tier'. Thanks. Regards.