Transfer Manager v2 downloader concurrency fix and version control

[wty-Bryant]

v0.1 transfer manager v2's GetObject API needs user to initialize a concurrent reader and pass it to input for data downloading, this PR changed the concurrency design of new reader so user could call transfermanager.GetObject in the same way they call s3.GetObject and retrieve response data directly from output body like this:

svc := transfermanager.NewFromConfig(s3Client, cfg) out, err := svc.GetObject(ctx, input) written, err := io.Copy(dst, out.Body) 

Besides concurrency fix, this pr also add version control to DownloadObject and GetObject in the same way of #3050 in old transfer manager