## Motivation and Context
- #1925 

## Description
This adds a minimal Hyper client, focusing on not exposing any unstable
APIs. For this reason, the `Client::Builder` customization API is not
exposed anymore. We do this because at some point in the future, we will
likely move away from the hyper-util based Client.

The code for this was lifted directly from the Hyper 0.14 implementation
but updated for new traits.

However, this does come with some new valuable pieces:
1. Support for aws-lc (no FIPS yet)
2. Support for providing a custom DNS resolver

## Testing
- E2E test with Hyper. A Canary should also be added
(https://github.com/awslabs/aws-sdk-rust/issues/1089)

## Checklist
<!--- If a checkbox below is not applicable, then please DELETE it
rather than leaving it unchecked -->
- [ ] I have updated `CHANGELOG.next.toml` if I made changes to the
smithy-rs codegen or runtime crates
- [ ] I have updated `CHANGELOG.next.toml` if I made changes to the AWS
SDK, generated SDK code, or SDK runtime crates

----

_By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice._