## Motivation and Context
<!--- Why is this change required? What problem does it solve? -->
<!--- If it fixes an open issue, please link to the issue here -->
This change adds a new crate, `aws-smithy-wasm`, that exports a SDK
compatible WASI http client. This is a continuation of the work in #2520
using the now stabilized WASI 0.2.0 interfaces from the [wasi
crate](https://crates.io/crates/wasi). This supports, but does not
finalize the work for #2087

## Description
<!--- Describe your changes in detail -->

Add a new crate, `aws-smithy-wasm` which exports a function
`wasi_http_client` that will provide the user with a WASI compatible
http client. This client is implemented by using the
`wasi::http::outgoing_handler`
[ref](https://docs.rs/wasi/0.12.0+wasi-0.2.0/wasi/http/outgoing_handler/index.html

)
along with some utility implementations of `TryFrom` to transform back
and worth between the types from the `http` crate and the `wasi::http`
types. It also exports a unit struct `WasmSleep` that impls the
`AsyncSleep` trait needed by the SDK.

## Testing
<!--- Please describe in detail how you tested your changes -->
<!--- Include details of your testing environment, and the tests you ran
to -->
<!--- see how your change affects other areas of the code, etc. -->
This is tested via an integration test in
`aws/sdk/integration-tests/webassembly` that uses the wasi http-client
to vuild a config and an operation (that is not sent). It is further
tested in a new canary (`wasm_canary`) that calls the S3
`list_objects_v2` API.

## 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

----

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

---------

Co-authored-by: Eduardo Rodrigues <eduardomourar@users.noreply.github.com>
Co-authored-by: Eduardo de Moura Rodrigues <16357187+eduardomourar@users.noreply.github.com>
Co-authored-by: ysaito1001 <awsaito@amazon.com>
Co-authored-by: John DiSanti <jdisanti@amazon.com>
Co-authored-by: Russell Cohen <rcoh@amazon.com>
Co-authored-by: John DiSanti <john@vinylsquid.com>