Remove fs stat and use bytesWritten as content length

[mejiaej]

Hi, as described in this issue. I want to avoid any potential fs.stat delay which can be caused by infrastructure such as EFS. The best way to do it is to remove any potential delay between the creation of the readStream and the HTTP request to the destination.

I found that this.bytesWritten contains the number of bytes of the file downloaded from a provider(google drive, one drive, etc.). And, because companion uploads that same file it is safe to use it as content-length when uploading. In fact, the code already uses this.bytesWritten as a synonym of bytesTotal

please let me know if there is anything that I didn't clearly explain.

cc @kvz this is a better solution than fs.statSync which I brought up on a previous PR that I closed.

[ifedapoolarewaju]

thank you!