Avoid making `FsBuilder` aware of http-body version at interface level (#3101)

## Motivation and Context
Follow up on #3088

## Description
This PR reverts `ByteStream::read_with_body_0_4_from`,
`ByteStream::from_path_body_0_4`, and `ByteStream::from_file_body_0_4`
to the old names since from a customers' point of view, `FsBuilder`
should not mention anything about an `http-body` version at the API
level.

`FsBuilder` is currently an opt-in feature (with `rt-tokio` enabled) and
we make it tied to `http-body-0-4-x` by requiring `rt-tokio` including a
dependency on `http-body` version 0.4.x.

## Testing
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

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