Strip names off most boundary lines at low and mid-zooms

[nvkelso]

We include default and localized name:left and name:right properties on boundary lines when the aren't used for labeling until later zooms. This bloats file size.

There are also hints in Natural Earth about the zoom they should start being labeled we can leverage.

[nvkelso]

SEO: boundaries layer

We could also follow the lead in #1693 and drop features and names (name and name:*) based on the NE min_zoom and min_label?

[nvkelso]

Looking around Switzerland I still see a lot of name variants that aren't labeled but there in the data, but overall this is working (as proved by the reduction in the boundary layer size) so I think it's just a parameter tuning opportunity in the next release, with possible incorporation of the Natural Earth zooms as it's not necessary to include both the label centroid and the line names at most zooms together.

8/47.132/8.432

Like:

[nvkelso]

This is mostly working, closing.