Provided timeout should be applied to all resumable upload requests

[amo12937]

I investigated ReadTimeout error that is thrown in Client.load_table_from_json.

The error occurred at ResumableUpload.transmit_next_chunk in _do_resumable_upload in client.py.
Lookig at the code, timeout argument is passed to _initiate_resumable_upload but not to transmit_next_chunk, and the default timeout (which is 60 sec) will be used.
Is this intentional, or does anyone plan to fix it?
Thank you.

[plamut]

Hm... the line containing the transmit_next_chunk() code was written more than 4 years ago, while the support for customizable timeouts in resumable media's ResumableUpload class have only been added ~17 months ago. For some reason this hasn't been leveraged in the BigQuery client (yet?).

The timeouts were added to several BigQuery methods 13 months ago in #327, including the change to _initiate_resumable_upload(), but the upload.transmit_next_chunk(...) call was left intact.

@tswast Do you maybe remember if there was a specific reason for that?
I was on a short sabbatical back then, so I can't say, but there's nothing on the PR either, thus it seems like an oversight to me.

[tswast]

I don't recall a specific reason. Agreed that it's most likely just an oversight