Remove `futures_core::stream::Stream` from `aws_smithy_http::byte_stream::ByteStream` (#2983)

## Motivation and Context
Removes `futures_core::stream::Stream` from
`aws_smithy_http::byte_stream::ByteStream`

## 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
`aws_smithy_http::byte_stream::ByteStream`. To continue support existing
places that relied upon `ByteStream` implementing the `Stream` trait, we
provide explicit `.next`, `.try_next`, and `.size_hints` methods on that
type. As part of it, a doc-hidden type `FuturesStreamCompatByteStream`,
which implements `Stream`, has been added to `aws_smithy_http` to cater
to those who need a type implementing `Stream` (see
[discussion](https://github.com/awslabs/smithy-rs/pull/2910#discussion_r1317112233)
why doc-hidden).

Another place we need to update is codegen responsible for rendering
stream payload serializer, and this affects the server. The regular
server and the python server have slightly different rendering
requirements, since the former uses
`aws_smithy_http::byte_stream::ByteStream` (that does _not_ implement
the `Stream` trait) and latter uses its own
[ByteStream](https://github.com/awslabs/smithy-rs/blob/cb79a68e3c38d1e62d3980d5e7baedc1144bacc7/rust-runtime/aws-smithy-http-server-python/src/types.rs#L343)
(that does implement `Stream`). We use
`ServerHttpBoundProtocolCustomization` to handle the difference:
`StreamPayloadSerializerCustomization` and
`PythonServerStreamPayloadSerializerCustomization`.

## Testing
No new behavior has been added, relied on the existing tests in CI.

## Checklist
- [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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