Intent to ship: Iterator Helpers

[Daniel Minor]

As of Firefox 130 I intend to turn Iterator Helpers on by default. It has been developed behind the preference `javascript.options.experimental.`. The proposal is currently at Stage 3 of the TC39 process. It has been implemented in V8 (https://issues.chromium.org/issues/42203505) and some work is under way in JSC (https://bugs.webkit.org/show_bug.cgi?id=248650).

Bug to turn on by default: https://bugzilla.mozilla.org/show_bug.cgi?id=1896390

Standard: https://github.com/tc39/proposal-iterator-helpers

[Daniel Minor]

Quick correction, the pref is `javascript.options.experimental.iterator_helpers`.