[request]: A crate similar to serde_dynamo

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**Tell us about your request**
[serde_dynamo](https://docs.rs/serde_dynamo/2.4.0/serde_dynamo/index.html) provides a way to serialize and deserialize between data stored in these Items and strongly-typed Rust data structures. Would be nice to have something similar for aws-sdk-rust.

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
Currently my team is switching from using rusoto to aws-sdk-rust. One part of our code is to deserialize the items from DynamoDb with serde_dynamo::[from_items](https://docs.rs/serde_dynamo/2.4.0/serde_dynamo/fn.from_items.html) but can no long us this because `from_items` uses rusoto _AttributeValue_. I searched for something similar in aws sdk rust docs but couldn't find anything.

**Are you currently working around this issue?**
I would need to recreate what serde_dynamo::from_items does.

**Additional context**
N/A

**Attachments**
N/A

Start by comparing serde_dynamo::from_items with the aws-sdk-rust DynamoDB Item and AttributeValue types, then review the AWS SDK Rust documentation for an equivalent conversion entry point. Done means providing serde-compatible serialization and deserialization for DynamoDB items without depending on rusoto AttributeValue.

Written by the indexing model from the issue text.