Ruleset defined Pearl Harbour firepower
There are other cases where firepower is set to hardcoded 1. All of them should be ruleset controlled, not just the Pearl Harbour rule.
We should rename combat bonus "FirePower1" before making the firepower in fact *not* 1 -> #43075
As civ1 didn't have hitpoints, we currently set them to 1 - unit dies when ever it's hit. The very low hit point count has been shown to cause other problems (mainly with AI considering all units extremely weak). There has been ideas around that the hitpoint count in civ1 should be increased, with associated increase to every unit's firepower so that they would still kill anything with one hit. This is currently prevented by the fact that Pearl Harbour rule *hardcodes* firepower of 1. Make that firepower too ruleset controllable.