Fix penentrating strike

[ampersand55]

Summary

Bugfixes "Fix penetrating strike"

Purpose of change

Correction of my previous PR #77812.

I misunderstood how "arpen" worked and the technique ended up doing nothing as it just increased the default armor penetration 0 by 33%. I also didn't do enough testing to catch the error.

Describe the solution

There is no good way to increase armor penetration linearly, and how it's applied and how it interacts with weakpoints and crits (pierce crits have 33% armor penetration) is quite complicated, so I derived at a value after testing, which is a flat bonus to armor penetration of 2x melee skill.

As it scales scales with melee skill and adds a flat armor penetration value, it's especially strong for a character with high melee skill using a low damage weapon. When balancing, I've assumed a character with 0-3 melee skill has a wooden spear, a character with 4-6 melee skill has a knife spear and a character with 7+ melee skill has a qiang.

A 2 melee skill character with a wooden spear (18 pierce) that crit for 2x damage would do 36 base pierce damage + 4 armor penetration.

A 5 melee skill character with a knife spear (26 pierce) that crit for 2x damage would do 52 base pierce damage +10 armor penetration.

A 10 melee skill character with a qiang (43 pierce) that crit for 2x damage would do 86 base pierce damage +20 armor penetration.

Describe alternatives you've considered

Changing it to a stun, like the other weapon categories have.

Testing

Made a 8/8/8/8 debug characters with 5 or 10 in all skills, using wooden spears, knifes pears or qiangs and tested it against 55 zombie cops and 55 zombie soldiers.

Here screenshots of the damage log comparing a 8/8/8/8 character with 5 in all skills using a knife spear with penetrating strike and one with a generic crit technique against a zombie cop (6 armor):

There was a minimal change in damage against zombie soldiers with 20 stab armor.

Additional context