Perf: avoid any reprojection for input datasets in EPSG 4326 or web mercator

[kylebarron]

I think we should be able to do everything on the GPU here?

Related to #41, but that's the general case, where it's maybe faster to reproject input sources to web mercator than to 4326?

[kylebarron]

It should be similar to how the MVT layer renders from local web mercator coordinates instead of doing CPU work to convert to screen space.

https://github.com/visgl/deck.gl/blob/2edcc0dde1bbc9a93fdfc4b52dfea0daf1f3c68b/modules/geo-layers/src/mvt-layer/mvt-layer.ts#L265-L270