Improve performance when zooming in and out

[cmdcolin]

Currently zooming in and out is less performant than scrolling side to side

There are probably several different factors that come into play with this, for example, it totally redoes the getFeatures calls, and the layout, and more

It is worth comparing with IGV for relative performance, which is pretty snappy

[cmdcolin]

this refers not necessarily to the zoom animation, just the plain aspect of rendering after a zoom level change

[cmdcolin]

A recent discussion during a weekly meeting (maybe two weeks ago) had us look at a demo that @garrettjstevens did, where the apollo track had a fast re-render after zoom (basically instant), and even demoed continuous re-render at every frame during a zoom out instead of stretching the image, which was pretty cool

We agreed that the user experience is very good with this, and it may be valuable to invest in doing this for more track types.

This branch is investigating how it could be added to alignments track potentially https://github.com/GMOD/jbrowse-components/tree/new_pileup_refactor