Update with new iPyWWT widget

[nmearl]

I've recreated the ipywwt widget to align more fully with the features of the original pywwt widget. In doing so, the SelectionTool has been refactored to be a full Solara component. Likewise, some changes have occurred for the DistanceTool component as well (though it remains ipywidget-based).

With the new ipywwt widget, there is a clear callback defined for when the wwt front-end is finished loading and ready to receive messages. This has allowed for implementing a loading spinner before rendering, as well as for removing some of the timers we had implemented to attempt awaiting the state of the wwt front-end.

We also now mount the wwt app in its own iframe, which requires having a separate process for hosting a local WWT instance. This instance will be used for any other widget which references the WWT research app.

This also seems to have resolved issues #840 and #447, but I encourage others to pull down this PR and give it a spin.

[patudom]

Awesome!!! Thanks so much @nmearl. So far, I've consistently gotten the green dots on this PR, but it's hard to tell for sure if it's fixed because the issue is so intermittent. I think we'll have to trial this fix for a while before we know for sure that the problem has gone away for good.

I think WWT is missing a few things it needs - I'm getting DSS now instead of SDSS. @Carifio24, can you please make the relevant updates so we can merge this to the deployed demo?

(ETA: the Stage 3 distance tool seems to be behaving as it did before).

Thanks!