S3 Legacy Rust

[DavidSouther]

Pulling together #3609 and #4085

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#3609

I'd really like to see a zero-copy, async (tokio) streaming example for the s3 get_object api which lets me send each line in a file to a channel for processing large files. This is really useful in a datapipeline scenario: collecting metrics, data statistics, pushing the data to a different service, transformations, etc.

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#4085

Create an example that demonstrates that for a PutObject request. The resulting body should be "retryable."

Checksums are implemented with body wrappers and can probably be adapted.

Checksum body wrapping fn
Checksum retryability test
SdkBody::map is the easiest way to wrap a body
What does this example accomplish?
This example will teach users how to use body wrappers in order to track the progress of uploads.

[github-actions]

Marked stale by the Shirriff. Notifying @awsdocs/aws-sdk-docs-code-maintainers

[DavidSouther]

Done w/ #4696