Deprecate and remove JS array buffer version

[jerch]

Reminder issue to deprecate and the remove the JS array based buffer implementation. Part of #791.

Currently the JS array based buffer line blocks several cleanups/features to come:

• Edit: moved into separate tracking issue upcoming corelib changes with the new buffer #1920

@Tyriar Can we make the typed array version the default in 3.9 yet, and deprecate the JS array thing? And maybe remove the JS array version afterwards? This way we have at least one release with both versions and the typed array as default. I feel abit uneasy about a quick removal of the JS array version, but its kinda needed to get some progress with the list above.

/cc @mofux @bgw

[Tyriar]

Can we make the typed array version the default in 3.9 yet, and deprecate the JS array thing?

I'm fine with that. Removal will need to wait until at least 3.10.0 though, we need to be careful as it will be too hard to bring it back once we remove it.

[jerch]

Relocated TODO list into tracking issue, closing issue.