port https://github.com/mapbox/mapbox-gl-js/pull/4781
This improves legibility of labels that follow lines in pitched views.
The previous approach used the limited information in the shader to
calculate put the glyph in approximatelyright place. The new approach
does this more accurately by doing it on the cpu where we have access to
the entire line geometry.
Viewport-aligned curved labels start to look very strange in the distance. Until we have a better system for projecting them, just prevent them from showing.
We're storing GeometryTileFeature objects in SymbolLayout, but they may reference data in GeometryTileLayer, which could go away if we don't retain it.
