Move `result` and `connection` from `aws-smithy-http` to `aws-smithy-runtime-api` (#3103)

## Motivation and Context
Implements #3092 

## Description
This PR moves the `connection` and `result` modules from
`aws-smithy-http` to `aws_smithy_runtime_api`. `SdkError` is primarily
used within the context of the orchestrator, hence
`aws_smithy_runtime_api` instead of `aws-smithy-types`.

Like the previous sibling PRs, type aliases for affected pub items are
left in `aws_smithy_http` for backwards compatibility. However, due to
lack of trait aliases, a trait `CreateUnhandledError` needs to be
consumed from `aws_smithy_runtime_api`.

This PR also updates existing places that consumed those moved types so
they now depend on `aws-smithy-runtime-api` to do so.

## Testing
Relied on the existing tests, which ensured no deprecated warnings of
using moved types from the old place were issued.

## Checklist
- [x] I have updated `CHANGELOG.next.toml` if I made changes to the
smithy-rs codegen or runtime crates

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