When retrying a request with an `IO` object as `data`, rewind the filehandle before each retry

Cf. [`rewind_body()`](https://github.com/psf/requests/blob/88dce9d854797c05d0ff296b70e0430535ef8aaf/src/requests/utils.py#L1081) and its invocations in `requests`

Cf. [`rewind_body()`](https://github.com/urllib3/urllib3/blob/b8589ec9f8c4da91511e601b632ac06af7e7c10e/src/urllib3/util/request.py#L154) and its invocations in `urllib3`