Scope the Tile worker thread to an Environment

We are also removing the code that is passing the Environment around
and instead, we get now the Environment in the TileData using
Environment::Get().

When processing the job, the work will be temporally registered to
the Environment as "TileWorker_0/0/0" which can be used for logging
in the future. At the end of the job, it gets unregistered
automatically from the Environment.

src/mbgl/map/raster_tile_data.cpp

@@ -5,8 +5,8 @@
 using namespace mbgl;
 
 RasterTileData::RasterTileData(Tile::ID const &id_, TexturePool &texturePool,
-                               const SourceInfo &source_, Environment &env_)
-    : TileData(id_, source_, env_), bucket(texturePool, layout) {
+                               const SourceInfo &source_)
+    : TileData(id_, source_), bucket(texturePool, layout) {
 }
 
 RasterTileData::~RasterTileData() {