Missing coverage: "next" only accessed once for iterator in IterableToList

[anba]

We currently don't have coverage for tc39/ecma262#988 for the iterator in IterableToList.

Found while working on https://bugzilla.mozilla.org/show_bug.cgi?id=1407588.

[littledan]

I don't think we have much coverage of tc39/ecma262#988 for for-of loops or almost anything else using the iteration protocol, for that matter. The change has not yet landed in V8, but when updating test262 to the latest version, the only tests I see updated are for the async-from-sync iterator, updated in 1144b5a (thanks, @caitp!). cc @kmiller68

[caitp]

There's f3b5a1e which includes an update to a for-of test, and 0881a6a which includes an update to an async yield* tests, as well as the async-from-sync tests.

But, it seems like there isn't the same style of coverage for ES6 yield*, or for-await-of tests, or spread operations, etc

[littledan]

My mistake; these tests were checked in earlier than the other ones, and I didn't notice that they were already marked as failing in V8.