Fix progress parameter type compatibility between cURL and StreamHandler (#2936)
Fix progress parameter type compatibility between cURL and StreamHandler (#2936)

Unknown values of the progress called are filled with `0` by cURL and in fact
the `CURLOPT_PROGRESSFUNCTION` parameters are explicitly typed `int` in
CurlFactory.

StreamHandler always provided `null` as the upload progress, because the
progress is not known there. Adjust this to `0` for consistent behavior.
guzzle/guzzle,michabbb-backup/guzzle,guzzle/guzzle,michabbb-backup/guzzle