[0.17.4] Biter attack scaling in campaign

[appenz]

I think right now in the campaign, biter attacks scale to quickly for novice players. Biters spawns for me quickly scales to about 20 new biters per second attacking in waves of 20 from each side every 2 seconds. 4 Assembly Machines producing ammunition were unable to keep up with ammo consumption. With a fairly aggressive build (8 science labs, 4 ammo production all running at full speed) at the second site, ammo consumption quickly outstripped production capacity and I was overwhelmed before I could complete research for logistics science pack.