By the way of D8959, performed some minor cleanups in blob codebase.
1. Recently noticed that `aws_sdk_{dynamodb,s3}::Client` already have `Arc` inside, so we don't need to wrap it with `Arc` again.
2. Also deleted unnecessary `aws_types` dependency. The type we're using is already included in `aws_client`.
> It probably wasn't in the past and that's why it was added, but now it's not needed anymore.
Plus some very minor fixes to fix Clippy warns.
Depends on D8959