Reduce special casing in StructureCatalogue::get

[DanRStevens]

There are currently a few special cases in StructureCatalogue::get that can probably be removed:

---

There is some inconsistency with setting the lander tile for the SeedLander:

case StructureID::SID_CARGO_LANDER: // only here for loading games
	structure = new CargoLander(tile);
// ...
case StructureID::SID_COLONIST_LANDER: // only here for loading games
	structure = new ColonistLander(tile);
// ...
case StructureID::SID_SEED_LANDER: // only here for loading games
	structure = new SeedLander({0, 0});

---

The MineFacility is constructed with a nullptr for the Mine*:

case StructureID::SID_MINE_FACILITY: // only here for loading games
	structure = new MineFacility(nullptr);

Potentially the tile could be used to find the Mine*, which could be set using the MineFacility constructor. It may be possible to remove the MineFacility::mine setter function. This would need some coordination with MapViewState::readStructures, which also uses the mine setter function. Though earlier there is a call to StructureCatalogue::get which could have set the Mine*:

auto& structure = *StructureCatalogue::get(structureId, &tile);
// ...
if (structureId == StructureID::SID_MINE_FACILITY)
{
	auto* mine = mTileMap->getTile({mapCoordinate.xy, 0}).mine();
	if (mine == nullptr)
	{
		throw std::runtime_error("Mine Facility is located on a Tile with no Mine.");
	}

	auto& mineFacility = *static_cast<MineFacility*>(&structure);
	mineFacility.mine(mine);
	// ...

---

There is a comment on MineShaft that indicates a special case:

case StructureID::SID_MINE_SHAFT: // only here for loading games
	structure = new MineShaft();

Looking into this, it seems that structure is specially created with direct uses of new in Robominer::buildMine and MapViewState::onMineFacilityExtend. Perhaps these methods should be updated to use StructureCatalogue::get for consistency.