Remove `futures_core::stream::Stream` from `aws-smithy-async` (#2978)

## Motivation and Context
Removes `futures_core::stream::Stream` from the `aws-smithy-async`
crate.

## Description
This PR is part of our ongoing effort,
https://github.com/awslabs/smithy-rs/issues/2413. We remove the
`futures_core::stream::Stream` trait from the public API in the
`aws-smithy-async` crate. While doing so, we compensate
- `FnStream` by providing the explicit `.next` and `.collect` methods to
let the previously working code continue working.
- `TryFlatMap` by making it return a new-type wrapper `PaginationStream`
to hide `FnStream` from those who use paginators.

With this change, the latest canary no longer uses
`tokio_stream::StreamExt`, since the paginator does not work in terms of
the `Stream` trait. Furthermore, `aws-sdk-rust` has been more than [3
releases since
release-2023-01-26](https://github.com/awslabs/aws-sdk-rust/releases),
so the module `release-2023-01-26` has been removed from
`canary-lambda`.

## Testing
No new tests added, but made sure the existing tests keep working with
the change.

## 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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