Feature: Stalled stream protection (#3202)

[See the upgrade guide for this feature to learn
more.](https://github.com/awslabs/aws-sdk-rust/discussions/956)

The breaking change is to the `MinimumThroughputBody::new` method.

## Motivation and Context
<!--- Why is this change required? What problem does it solve? -->
<!--- If it fixes an open issue, please link to the issue here -->
#1562

## Description
<!--- Describe your changes in detail -->
https://github.com/awslabs/aws-sdk-rust/discussions/956



## Testing
<!--- Please describe in detail how you tested your changes -->
<!--- Include details of your testing environment, and the tests you ran
to -->
<!--- see how your change affects other areas of the code, etc. -->
I added several tests

## Checklist
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rather than leaving it unchecked -->
- [x] I have updated `CHANGELOG.next.toml` if I made changes to the
smithy-rs codegen or runtime crates
- [x] I have updated `CHANGELOG.next.toml` if I made changes to the AWS
SDK, generated SDK code, or SDK runtime crates

----

_By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice._

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Co-authored-by: John DiSanti <jdisanti@amazon.com>
Co-authored-by: Russell Cohen <rcoh@amazon.com>