behavior version 2024-03-28 (#3617)

## Motivation and Context
This PR is the combination of two previously reviewed PRs that both
enable new behaviors behind a new Behavior Major Version (BMV):
* https://github.com/smithy-lang/smithy-rs/pull/3527
* https://github.com/smithy-lang/smithy-rs/pull/3578



## Description
* Enables stalled stream protection by default on latest behavior
version.
* Enables creation of a default identity cache.

## Testing
All testing done on prior PRs. See for details.

## Checklist
<!--- If a checkbox below is not applicable, then please DELETE it
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

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_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: ysaito1001 <awsaito@amazon.com>