Progress bar for file transfers

[quinnwai]

Is your feature request related to a problem? Please describe.
Users don't know how long an upload will take. Adding a progress bar is non-trivial since we can't just use gen3-clients's progress bar which logs it to stdout. We will need to edit gen3-client to pass the bytes from the nested calls as a callback in git drs so that we can return a ProgressResponse to LFS.

Describe the solution you'd like
Progress bar provided by LFS will be updated as expected.

Describe alternatives you've considered
Writing to the transfer.log file directly. This would unnecessarily log a line per update which could get cumbersome.

Additional context
Add any other context or screenshots about the feature request here.

[quinnwai]

possible design: gen3-client passes a callback to git drs containing the current bytes so that git drs can send a progress message back to git lfs.

// in gen3-client
func uploadFile(furObject commonUtils.FileUploadRequestObject, retryCount int, sendUpdate func(current, total int64)) error {
	log.Println("Uploading data ...")
	furObject.Bar.Output = io.Discard // Uncomment to suppress progress bar output
	furObject.Bar.Start()

	if sendUpdate != nil {
	furObject.Bar.Callback = func(out string) {
		sendUpdate(furObject.Bar.Get())
	}
	}
	client := &http.Client{}
	resp, err := client.Do(furObject.Request)

[matthewpeterkort]

implementing in #232

[matthewpeterkort]

implemented in #232