Rename Fetch request streams to Fetch upload streaming?

[foolip]

@daisuke-e and @yoichio have raised that Fetch request streams might be more natural to call Fetch upload streaming.

The Chromium bug and Chromestatus entry called it upload streaming:
https://chromestatus.com/feature/5274139738767360
https://issues.chromium.org/issues/40505032

On the other hand, https://developer.chrome.com/docs/capabilities/web-apis/fetch-streaming-requests called it "Streaming requests with the fetch API" which is closer to the current name.

@captainbrosset @ddbeck discussed naming a bit in #2517, but AFAICT not this option.

What name is most familiar to web developers?

[ddbeck]

This came up on the WebDX call. My take was that renaming the name field is fine and good. I wasn't very familiar with the feature when I originally helped name it. I do have a small preference toward not using a gerund (as in "Fetch upload streams"), but I don't feel very strongly about it. I opened #2898 anyway.

If we wish to change the ID to match (fetch-request-streams → fetch-upload-streams), then we'd have to wait for #91 to resolve this.