Describe the new feature:
Many popular sites like Github and Discord use AbortController even if they don't really call abort method most of the time. Right now we have a stub in #34519 and prior work in #32871. It's better if we could finish this WebAPI eventually.

TODO:

• Implement the basics of AbortSignal Implement AbortSignal basics #36935
• Finish current stub for AbortController
• Use in https://streams.spec.whatwg.org/#writablestreamdefaultcontroller-abortcontroller
• Use in https://streams.spec.whatwg.org/#readablestream-pipe-to-signal
• Use in https://fetch.spec.whatwg.org/#request-signal
• Use in https://dom.spec.whatwg.org/#event-listener-signal
• Turn on AbortController in WPT (Add AbortController to experimental web platform features #39904)
• Identify other specs implemented by Servo using a signal.