Simplify geometry of low zoom Natural Earth features

[nvkelso]

At low zooms we don't currently simplify geometries, but we should. This will produce smaller file size.

Historically we've relied on switching back and forth between different Natural Earth scale sets (110m, 50m, then 10m), and that mostly works. But on the first zoom each of those are introduced that produces too much geometry, then on the next zoom it's a little bit much, and next next zoom it's usually fine (or we switched to the next NE scale set).

It may be a simple as setting these simplify_start zooms to 0, but there is a lot of OSM mixed up in those configs, so we might want to split the config for NE from OSM, too.

• water layer: https://github.com/tilezen/vector-datasource/blob/master/queries.yaml#L152-L167
• earth layer: https://github.com/tilezen/vector-datasource/blob/master/queries.yaml#L168-L181
• roads layer: https://github.com/tilezen/vector-datasource/blob/master/queries.yaml#L214-L238
• boundaries layer: https://github.com/tilezen/vector-datasource/blob/master/queries.yaml#L286-L302

[nvkelso]

Fixed via #2015.