[DOM4] NodeList should be deprecated

Dynamic NodeLists have a significant memory and performance cost. Static
NodeLists are basically just under-powered arrays. We should just return
Node arrays from any new APIs that return a list of Nodes. I'd like to see
NodeList get similar treatment to hasFeature, i.e. a note that it not be
used for new APIs and possibly even the explicitly list the APIs allowed to
return them.

I don't see the Dynamic/Static distinction in DOM4 or the HTML spec. Is
this specified anywhere?

For reference, this came up in WebKit with some new Regions APIs
https://bugs.webkit.org/show_bug.cgi?id=80638.