SAWS: tweak tech costs

[GinjaNinja32]

• max_tech_cost: was 500, now random-range-low-100-10000 to match base Factorio random-range-low-200-10000 on non-ramping slots, random-range-1000-5000 on ramping ones
• tech_cost_mix: was 100, now 20% 100, 80% random; base Factorio is random
• ramping_tech_costs: was false, now 20% true, 80% false to match base Factorio 50/50

Not 100% sure I like the ramping costs being 80% false, but going to what base Factorio does is probably at least a decent starting point.