implement doit(): resumable media upload

[Byron]

Something to consider here is how the delegate is involved to store the upload information to allow actually resuming it in another call.
Supporting this might ripple through our method builder a bit, as it might need more information to allow this. Or the delegate provides it at runtime, which would certainly be prepared.

Goal is to support storing the current result, and resuming a few minutes/hours later without issues, i.e. the API must allow to do that natively.

[Byron]

You can watch the development stream in multiple parts

• infrastructure and lifetimes
• simplification
• delegation
• header-hassle
• oauth2 scheme
• content-range header
• query upload status()
• resumable upload()
• cancellation support