[sda-cli] Provide feedback more promptly when recursively uploading a folder with many large files

[nanjiangshu]

Please describe the feature
As a user, I want sda-cli to provide feedback more promptly when recursively uploading a folder with many large files, so that I can understand the program is running properly.

Currently, the upload sub-command encrypts all files before uploading, and users may encounter situations where the program seems to hang for many hours.

One possible solution is to process one file at a time.

Acceptance criteria

Additional context

Estimation of size: small

Estimation of priority: medium