Consolidate fluent client builder implementations (#668)

* Consolidate fluent client builder implementations

* Rename FluentClientDecorator to AwsFluentClientDecorator

* Remove potentially confusing Smithy details from AWS fluent clients

* Fix AWS client generics issue

* fix missing template param

* remove problematic whitespace

* Fix Clone derivation issue

* Fix unintentional removal of `from_conf_conn`

* Change `Standard` to `retry`

Co-authored-by: Russell Cohen <rcoh@amazon.com>