[2.1.14] Expose circuit_connector_layer for more prototypes

[hgschmie]

Currently, circuit_connector_layer is only available for LoaderPrototype, CraftingMachineGraphicsSet and MiningDrillGraphicsSet. It may be useful to expose this for more prototypes. Specifically I am looking for the InserterPrototype.

(I am still occasionally poke at viewtopic.php?t=134043 and try to figure out whether this is solvable in the game. So far I had no luck).

Is there any information / guarantee on how overlapping entities are rendered? Are they rendered one-by-one (all layers of entity a first, then all layers of entity b) or layer by layer (first entity A layer 1, then entity B layer 1, then layer 2 and so on till 255)?

[boskid]

Implemented for 2.1.15.

Modding:
- Added CircuitConnectorSprites::render_layer and secondary_draw_order.
- Circuit connector for inserter no longer defaults to drawing on "floor" render layer.
- Circuit connector for train stops no longer defaults to drawing on "train-stop-top" render layer.
- Circuit connector for asteroid collector no longer defaults to drawing on "higher-object-under" render layer.
- Circuit connector for rocket silo no longer defaults to drawing with secondary draw order of 70.
- Removed LoaderPrototype::circuit_connector_layer. Use CircuitConnectorSprites::render_layer instead.
- Removed RailSignalPictureSet::circuit_connector_render_layer. Use CircuitConnectorSprites::render_layer instead.
- Removed CraftingMachineGraphicsSet::circuit_connector_layer and circuit_connector_secondary_draw_order. Use CircuitConnectorSprites::render_layer and secondary_draw_order instead.
- Removed MiningDrillGraphicsSet::circuit_connector_layer and circuit_connector_secondary_draw_order. Use CircuitConnectorSprites::render_layer and secondary_draw_order instead.

[hgschmie]

Cool. Thank you.