Improve generated documentation (#779)

* Fill in missing generated documentation for S3

* Document the `smithy-types` runtime crate

* Fix wildcard imports

* Normalize doc notes

* Fix some CI issues

* Incorporate feedback

* Fix `EnumGeneratorTest`

* Fix more CI issues

* Fix server codegen tests

* Fix more doc issues

* Update changelogs

* Update aws/SDK_CHANGELOG.md

Co-authored-by: Russell Cohen <russell.r.cohen@gmail.com>

* Update aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/AwsEndpointDecorator.kt

Co-authored-by: Russell Cohen <russell.r.cohen@gmail.com>

* Run pre-commit on all Kotlin files

* Use `emptySection`

* Fix namespace in doc comments