Feat S3 Transfer Manager v2 UploadDirectory

[wty-Bryant]

Implement v2 s3 transfer manager's UploadDirectory api bound to single union client which mimics normal service client's initialization and api call. User could now upload a directory's files recursively/non-recursively to S3 with customized filtering and key naming in a single operation call.

Test: This PR passed unit tests for UploadDirectory which covers use cases with different config and folder structure to confirm this key-prefix uploader could find valid file location, generate correct key and pass upload requests to S3 concurrently. It also passed integration test which uploads source directory containing different sizes files to S3 via new directory uploader, then downloads objects back using S3 client and checks their content consistency