Correctly display pain penalties.

[osuphobia]

Summary

Bugfixes "Correctly display pain penalties."

Purpose of change

Fix #72854

Describe the solution

After calculating and applying the pain penalties, save the numbers, then read them when displaying under EFFECTS in the character window.
Also fix the stats of character can get lower than 1 by pain penalties.

Describe alternatives you've considered

Use get_stat_base instead of get_stat in Character::get_pain_penalty to calculate the penalties.

Testing

Compiled and tested locally.

Additional context

With 100 pain, stats are: 6/12 str, 3/12 dex, 1/12 int, 1/12 per, and the pain penalties are displayed correctly.

[osuphobia]

There is another issue existing, and I'm not sure if it can be fixed in this PR, or worth opening a separate PR.
That is, NPCs' stats are not actually affected by pain.
https://discord.com/channels/598523535169945603/598535827169083403/1244629105991876660
Seems that there is no need for me to do further adjustment right now.