Add onTap, queryRenderedFeatures, and remove boilerplate

[yoavrofe]

Now it's possible to query the map, using:

      onTap: (coordinates, offset) async {
        (List<dynamic> geoJson = await controller
            .queryRenderedFeatures(offset, layersToSearch, null);
      },

I refracted onMethodCall in MapboxPlugin.java to make it shorter and easier to understand.

Corrected some errors regarding device pixel ratio.

[Codex-]

Would be great to see this in, possible for mapbox to accept and make the tiny requested change? Looks like this PR has been forgotten about.

[tobrun]

@Codex- thank you for the ping on this, it's on my radar

[yoavrofe]

I fixed the error.