This change fixes the following problems:
1) Before this change, when multiple symbols were grouped close to the
tile borders, different tiles could place different symbols, because each
tile arbitrary assigned feature ids, and these ids defined the placement
order being applied. This caused artifacts at the tile boundaries.
With this change, in tile mode the placement order of two symbols crossing
a tile border is defined by their anchor `y` values. It means that the
symbols are being placed the same order across all the tiles.
2) Before this change, the engine did not place with priority the symbols
crossing the borders between two neighboring tiles. Now it does, and it
improves a lot symbol placement stability in the tile map mode.
* [test-runner] Setup iOS RenderTestRunner
* [test-runner] Make app runnable on firebase
* Add iOS platform dependent expectation and ignores; Run prepare script via cmake
* Make RenderTestRunner report test status
Move everything that might collect metrics to the metrics/ directory,
the only test manifests inside the render-test/ directory are the
unit tests of the probes.
