Enable crate reorganization for the SDK (#2433)

* Enable the crate reorg for the SDK

* Fix `aws-config`

* Fix SDK integration tests

* Fix event stream error module bug

* Fix doc test imports

* Fix some tests

* Fix external type check

* Fix the canary for both versions

* Fix codegen crash for certain SDK models

* Fix some doc compilation failures

* Update the changelog

* Fix presigning test merge conflict