Deprecate v1.x / merge 2.x into master

[springmeyer]

Currently the only (known) application depending on the v1 version of this library is MBGL. Once MBGL moves to vtzero (mapbox/mapbox-gl-native#11489) I propose we move forward with v2.x here by:

• merging v2.x branch (https://github.com/mapbox/vector-tile/tree/2.x) into master
• adding a deprecation note in the readme that using v1.x is no longer recommended for us
• adding a section of the readme that describes when you'd use vtzero vs mapbox/vector-tile
• consider renaming this repo to mapbox/libvectortile since mapbox/vector-tile is so easily confused given its generic name

Sound like a good plan? @flippmoke @kkaefer @anandthakker @joto

Context: v1.x of this library was never well tested. Vtzero is extremely well tested. The v2.x branch is now based on top of vtzero and is therefore a higher level, more robust replacement.

[anandthakker]

Capturing from chat, @flippmoke suggests that it might be preferable for MBGL to consume vector-tile (libvectortile) v2.x rather than using vtzero directly:

mapbox/vector-tile 2.x should be our connection between our geometry.hpp structures and vtzero I would hope, not in that it replaces or hides vtzero but provides fast and repeatable ways to use vtzero with geometry.hpp

[brunoabinader]

@springmeyer @flippmoke @joto @mapsam we have released geometry.hpp @ v1.0.0 last week, which among other changes no longer requires optional. Other depending libraries were also updated: geojson.hpp @ v0.4.3, geojson-vt-cpp @ v6.6.3 and supercluster.hpp @ v0.3.2.

For vector-tile, I've added a patch onto 2.x branch that updates the geometry.hpp version to 1.0.0, and I also have a working branch in mapbox-gl-native with all these changes in place: https://github.com/mapbox/mapbox-gl-native/tree/geometry-v1.0.0.

I would like to release the 2.x branch as-is, so we can proceed and update Mapbox GL Native accordingly. Any objections?

[brunoabinader]

Update: I was using vector-tile @ geometry-v1.0.0 branch which just updates the geometry.hpp version, without the rest of the 2.x branch changes, for the GL native branch I had working. With vector-tile 2.x, my branch need a bit more work as some more vector-tile types have changed internally.

[brunoabinader]

Given the current scenario, I wonder if it would be possible to temporarily update GL native to use geometry.hpp v1.0.0 by having it to use vector-tile @ geometry-v1.0.0` branch, while working on stabilizing 2.x.