Resizable/Growable (Shared)ArrayBuffers: Missing coverage for the "reload length" issue

[marjakh]

Spec bug: tc39/proposal-resizablearraybuffer#73

It would be great to have tests which fail if the implementation doesn't reload the length as the spec says.

[jugglinmike]

Thanks for the report! As of today, two observably-distinct solutions for the spec bug are under consideration (see tc39/proposal-resizablearraybuffer#74 and tc39/proposal-resizablearraybuffer#75). I'd like to hold off on writing tests until we have clarity on the expected semantics.