Ground radar quality update

[Qatavin]

Sooo, this whole time I've totally been forgetting to account for quality on the Ground Radar. Increased quality expands the apparent scan range that the radar seems to have, but the script that detects items on the ground remained the same. That has now been fixed.

The old system was random. It worked well enough, since there was plenty of time between attacks, but now the detection is orderly, going row by row. Also, a whole row of chunks is now scanned at once. Through extensive testing, I determined that we can save time by doing a smaller number of find_entities_filtered operations that cover more ground. The Ground Radar is now slower to compensate. I also reduced its normal range from 4 chunks to 2 (5 chunks x 5 chunks total). These are meant for picking up artifacts, which you can expect to be dropped quite close to your defensive perimeter. Half of 5 chunks of width is 80 tiles, which outranges even plasma turrets, so that should be plenty.

Ground scans will now also be staggered. The script will try to limit itself to only one scan per tick, or otherwise keep the number as low as feasible to avoid any potential lag spikes, such as might result if you set up a whole defensive wall and then power it up all at the same time. (In the event of a power loss, radars keep their scan progress, so that isn't an issue).

Overall, this new system has higher system demands, but is still within reason. I was able to run 100 legendary Ground Radars, which is far, far more than should ever been needed, and the time consumption at peak was only around 0.5 ms.