0.18.0 inserter optimizations for assemblers/furnaces should be done for labs as well

[uliko]

Before 0.18.0 inserters set up to pick up directly from belts did not go inactive when their target furnace/assembler was full of ingredients which made stuff like chest and belt stubs a common strategy to improve performance. The optimization in 0.18.0 made this unnecessary but it did unfortunately not include labs. If possible please perform the same optimization for labs as well.