Add a synchronous version of GeoJSONSource#setData

[lucaswoj]

Having a synchronous (main-thread) setData API dovetails nicely with the synchronous queryRenderedFeatures API. I see this API being useful in cases where

• very small GeoJSON sources need to be updated very quickly for animations
• users want to know exactly when a setData operation completes

previously implemented in #1979 as skipWorker

[ajfickas]

Any plans or workarounds for this?

I appear to be running into #2776 which this issue would appear to address.

I'm seeing features mysteriously disappear occasionally when zooming out for a GeoJSON source that is updated dynamically as the user repositions the map. Best workaround I have so far is to limit how often setData is called, but so far that means waiting a couple seconds between updates which significantly degrades the user experience.

[jdeboer-geoplan]

@ajfickas did you get anywhere with your issue? I'm also seeing the same issue as you

1. call setdata on a geojson source url that takes while to return
2. call setdata again on the source with a different url.
   The layer displays the second geoJSON and then the first overwrites it when it returns.
   I'm not sure a synchronous version is what I want I think I just want setData to abort any previous operation when it gets called again.

[ajfickas]

@jdeboer-geoplan My issue went away by upgrading to v0.43.0. However, my use case is was using setData to set a data object not a URL.