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.
Constants mask for data-driven paint properties is a reliable
criteria of whether the given updated properties can still be used
with the existing bucket (and the gl program instance).
