Add an option to turn off error handling

[kurin]

By default, b2 retries forever on error, which is the behavior specified in the Backblaze integration checklist.

However, this often breaks users who expect a command either to succeed or to fail. For example, in restic/restic#1906 a user ran an interactive command which ought to have finished after a few seconds, either indicating success or printing an error to the effect of "Backblaze is unavailable."

Currently users can set context deadlines, but this only tells the user that a deadline exceeded, and there's no indication about whether they did something wrong or why the command didn't succeed.

An option to turn off error handling would cease all such retries. It could either be a ClientOption, which would disable error handling for every request from that client, or a context wrapper, which would allow users to disable error handling on a per-request basis.