Propagate outer abort signal 'reason' to internal abort call

[AndreasPresthammer]

When outerSignal is in aborted state here

rxjs/packages/rxjs/src/internal/observable/dom/fetch.ts

Line 117 in c15b37f

if (outerSignal) {

it will call .abort() on the internal AbortController instance. The propagated abort call will cause the following error: AbortError: signal is aborted without reason. The outer signal might have a reason. I believe it would make sense to pass along the outerSignal.reason to the internal abort call. This would reduce confusion in error handling when the outer signal actually has a reason.

This applies to:

rxjs/packages/rxjs/src/internal/observable/dom/fetch.ts

Line 119 in c15b37f

controller.abort();