Before this change render passes were assigned for the
whole layer at properties evaluation stage.
This caused problems, as layer render data are bound
to the tile and these data might differ from tile to
tile, depending on which tile has been updated by the
tile worker and which has not been yet updated.
This change takes into consideration the actual render
passes required for each tile and combines them for
the layer render passes. Naturally, this change also
introduces render pass check for each render layer in
`RenderLayer::render()` implementations.
RenderTile and Tile will be split when ochestration movces to a separate thread.
This PR improves encapsulation of Tiles management: now performed within TilePyramid.
A RenderTile is already never created for a not renderable tile, guarantied by the checks in `updateRenderables()`.
However, the client code had plenty of `isRenderable()` checks in the render path, which complicated the code and affected rendering performance.
This patch removes the unneeded checks from the client code and puts an assertion to `TilePyramid::addRenderTile()`.
Before this change, `RenderSymbolLayer` with updated style was trying to render
symbols using the previous bucket (with paint property binders that matched a previous program).
Now, symbol bucket caches the latest corresponding paint properties (caching is happening on
complete tiles only). As a result, `RenderSymbolLayer` always picks the shader program and
its parameters in sync with the obtained bucket.
`LayerManager` is now responsible for `RenderLayer` instances creation,
so that there is a single entry point for creating of objects, which
correspond to a certain layer type.
The `LayerType type` field is dropped from `Layer::Impl`.
* Eliminates the need for EnableImmutableFromThis
* Eliminates the dependency of {Source,Layer}::Impl on corresponding Render class (circular dependency)
