More simplification to roads & boundary layers at zoom 9

[zerebubuth]

Context, this comment:

I suspect the roads and boundary layers need additional geom simplifying.

We could also strip some properties off the boundary layer at low zooms (like name and the name variants) at zooms less than 8 as the zoom isn't large enough to provide screen space to do the labeling.

@nvkelso: what would be an appropriate level of simplification for the roads & boundaries features?

[nvkelso]

This will be needed at both zoom 8 and 9 if we do the earlier NE to OSM switchover.

[nvkelso]

Let's try doubling the existing simplification and review.

Likley related to the generic simplify_and_clip function we pipe all layers thru.

[nvkelso]

We didn't see a huge drop in file size from this, but it did reveal an interesting bug we fixed.

No visual impact, closing.