Would have been nice to have serde_dynamo's feature within aws-sdk-dynamodb

### Describe the feature

`aws_lambda_events` currently uses `serde_dynamo`'s `AttributeValue` types instead of `aws-sdk-dynamodb`'s. Why don't `aws-sdk-dynamodb` introduce `serde_dynamo`'s code in inself, so that `aws_lambda_events` can deserailize the stream.

### Use Case

Right now its annoying to have to handle two types.

### Proposed Solution

_No response_

### Other Information

Maybe its `serde_dynamo` who should use `aws-sdk-dynamodb`'s `AttributeValue`?

### Acknowledgements

- [ ] I may be able to implement this feature request
- [ ] This feature might incur a breaking change

### A note for the community

### Community Note
* Please vote on this issue by adding a 👍 [reaction](https://blog.github.com/2016-03-10-add-reactions-to-pull-requests-issues-and-comments/) to the original issue to help the community and maintainers prioritize this request
* Please do not leave "+1" or "me too" comments, they generate extra noise for issue followers and do not help prioritize the request
* If you are interested in working on this issue, please leave a comment

Start by reading the aws_lambda_events DynamoDB stream handling and the aws-sdk-dynamodb AttributeValue types, then compare serde_dynamo's serialization and deserialization behavior. Determine whether the conversion belongs in aws-sdk-dynamodb or serde_dynamo, including compatibility and breaking-change implications. Done means the ownership decision and an agreed implementation scope are documented.

Written by the indexing model from the issue text.