Add more type aliases for types moved to the `aws-smithy-types` crate (#3091)

## Motivation and Context
https://github.com/awslabs/smithy-rs/pull/3076 missed type alias for
some types we moved to `aws-smithy-types`. This small PR will fix that.

## Testing
Relied on the existing tests in CI

## 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

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