Cleanup nations (Part 1) 🧹 (#2637)

## Description:

1. Using the wording `"Nation"`, `"FakeHuman"` and `"NPC"` at the same
time is confusing.
So I renamed every mention of `"FakeHuman"` and `"NPC"` in the entire
project to `"Nation"`. Just like they are called ingame.

2. `BotBehavior.ts` was originally intended for sharing the logic
between nations and bots.
But at the moment, the logic there isn't really shared and it's
basically just about attacking.
So I renamed `BotBehavior.ts` to `AiAttackBehavior.ts`. I use "Ai" to
indicate that this file is used by bots AND nations.

3. Moved `execuction/utils/AllianceBehavior.ts` to
`execuction/nation/NationAllianceBehavior.ts` to make sure everybody
understands that this file is not about alliances in general. It's just
about nations and how they handle alliances.

4. Removed `difficultyModifier` from `DefaultConfig`. It's unused and I
think we usually want to finetune the difficulty instead of using that
method.

5. Added `assertNever` in all `switch (difficulty)` default cases.

## Please complete the following:

- [X] I have added screenshots for all UI updates
- [X] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [X] I have added relevant tests to the test directory
- [X] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

FloPinguin

src/core/configuration/Config.ts

@@ -1,7 +1,6 @@
 import { Colord } from "colord";
 import { JWK } from "jose";
 import {
-  Difficulty,
   Game,
   GameMapType,
   GameMode,
@@ -82,7 +81,7 @@ export interface Config {
   theme(): Theme;
   percentageTilesOwnedToWin(): number;
   numBots(): number;
-  spawnNPCs(): boolean;
+  spawnNations(): boolean;
   isUnitDisabled(unitType: UnitType): boolean;
   bots(): number;
   infiniteGold(): boolean;
@@ -159,7 +158,6 @@ export interface Config {
   defensePostDefenseBonus(): number;
   defensePostSpeedBonus(): number;
   falloutDefenseModifier(percentOfFallout: number): number;
-  difficultyModifier(difficulty: Difficulty): number;
   warshipPatrolRange(): number;
   warshipShellAttackRate(): number;
   warshipTargettingRange(): number;

src/core/configuration/DefaultConfig.ts

@@ -287,19 +287,6 @@ export class DefaultConfig implements Config {
     return this._userSettings;
   }
 
-  difficultyModifier(difficulty: Difficulty): number {
-    switch (difficulty) {
-      case Difficulty.Easy:
-        return 1;
-      case Difficulty.Medium:
-        return 3;
-      case Difficulty.Hard:
-        return 9;
-      case Difficulty.Impossible:
-        return 18;
-    }
-  }
-
   cityTroopIncrease(): number {
     return 250_000;
   }
@@ -332,8 +319,8 @@ export class DefaultConfig implements Config {
     return this._gameConfig.playerTeams ?? 0;
   }
 
-  spawnNPCs(): boolean {
-    return !this._gameConfig.disableNPCs;
+  spawnNations(): boolean {
+    return !this._gameConfig.disableNations;
   }
 
   isUnitDisabled(unitType: UnitType): boolean {
@@ -712,7 +699,7 @@ export class DefaultConfig implements Config {
         mag *= 0.8;
       }
       if (
-        attacker.type() === PlayerType.FakeHuman &&
+        attacker.type() === PlayerType.Nation &&
         defender.type() === PlayerType.Bot
       ) {
         mag *= 0.8;
@@ -816,9 +803,9 @@ export class DefaultConfig implements Config {
   }
 
   useNationStrengthForStartManpower(): boolean {
-    // Currently disabled: FakeHumans became harder to play against due to AI improvements
+    // Currently disabled: Nations became harder to play against due to AI improvements
     // nation strength multiplier was unintentionally disabled during those AI improvements (playerInfo.nation was undefined),
-    // Re-enabling this without rebalancing FakeHuman difficulty elsewhere may make them overpowered
+    // Re-enabling this without rebalancing Nation difficulty elsewhere may make them overpowered
     return false;
   }
 
@@ -826,7 +813,7 @@ export class DefaultConfig implements Config {
     if (playerInfo.playerType === PlayerType.Bot) {
       return 10_000;
     }
-    if (playerInfo.playerType === PlayerType.FakeHuman) {
+    if (playerInfo.playerType === PlayerType.Nation) {
       const strength = this.useNationStrengthForStartManpower()
         ? (playerInfo.nationStrength ?? 1)
         : 1;
@@ -840,6 +827,8 @@ export class DefaultConfig implements Config {
           return 31_250 * strength;
         case Difficulty.Impossible:
           return 37_500 * strength;
+        default:
+          assertNever(this._gameConfig.difficulty);
       }
     }
     return this.infiniteTroops() ? 1_000_000 : 25_000;
@@ -873,6 +862,8 @@ export class DefaultConfig implements Config {
         return maxTroops * 1.25;
       case Difficulty.Impossible:
         return maxTroops * 1.5;
+      default:
+        assertNever(this._gameConfig.difficulty);
     }
   }
 
@@ -888,7 +879,7 @@ export class DefaultConfig implements Config {
       toAdd *= 0.6;
     }
 
-    if (player.type() === PlayerType.FakeHuman) {
+    if (player.type() === PlayerType.Nation) {
       switch (this._gameConfig.difficulty) {
         case Difficulty.Easy:
           toAdd *= 0.95;
@@ -902,6 +893,8 @@ export class DefaultConfig implements Config {
         case Difficulty.Impossible:
           toAdd *= 1.1;
           break;
+        default:
+          assertNever(this._gameConfig.difficulty);
       }
     }