Built-in AI: reject the promise if the abort signal was aborted

This CL fixes the abort signal handling for the APIs that return a
promise.

Previously it always throw an `AbortError` exception, but we should
reject the promise with the error from the abort signal according to
the spec.

Reference: https://dom.spec.whatwg.org/#abortcontroller-api-integration

Bug: 374879795
Change-Id: I19ddb16b6683bc2b76398f568f9625112a756702
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5953063
Reviewed-by: Tsuyoshi Horo <horo@chromium.org>
Commit-Queue: Mingyu Lei <leimy@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1373230}