[w3c/ServiceWorker] Filter out no-cors requests from the race-network-request (PR #1757)

This will address the comment in https://github.com/whatwg/fetch/pull/1737#issuecomment-2385734506.

When "race-network-request" is matched as the router rule, the service worker starts a network request in parallel with dispatching the fetch event. The response is keyed by request and managed in [race response map](https://w3c.github.io/ServiceWorker/#serviceworkerglobalscope-race-response-map). And the fetch API will check this map whether the request is already started by the service worker, and use its response if the corresponding entry is found.

We use [ok-status](https://fetch.spec.whatwg.org/#ok-status) to tell if the response is successful or not, and use the response only when the status is ok-status. This is needed to support the offline capability. However, with the request mode "no-cors", the response will be [filtered](https://fetch.spec.whatwg.org/#concept-filtered-response-opaque). The filtered response's status is always 0, so this is handled as a failure in "race-network-request" even without this change. But it would be better that we explicitly filter out "no-cors" in the handle fetch algorithm.

Once we get an agreement to this change, I'll add a WPT and fix Chrome behavior.


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  https://github.com/w3c/ServiceWorker/pull/1757

-- Commit Summary --

  * Filter out no-cors requests from the race-network-request

-- File Changes --

    M docs/index.bs (3)

-- Patch Links --

https://github.com/w3c/ServiceWorker/pull/1757.patch
https://github.com/w3c/ServiceWorker/pull/1757.diff

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