Mark train stations and factories as experimental (#1309)

## Description:

Train stations and factories won't be ready for v24.
Disable them by default. They can be reactivated on private lobies and
solo games, allowing us to gather feedbacks.

Changes:
- added an "experimental" attribute for units. When set, they are hidden
entirely when disabled, rather than appearing grayed out.
 - disabled train stations and factories by default.

Default values:

![image](https://github.com/user-attachments/assets/ec91ef80-c0ef-45a7-8e6c-6628a836b593)

No factories:

![image](https://github.com/user-attachments/assets/a3e35607-aed5-401c-bc38-4ea742d057c6)


## 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
- [x] I understand that submitting code with bugs that could have been
caught through manual testing blocks releases and new features for all
contributors

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

IngloriousTom

src/client/HostLobbyModal.ts

@@ -39,7 +39,10 @@ export class HostLobbyModal extends LitElement {
   @state() private copySuccess = false;
   @state() private players: string[] = [];
   @state() private useRandomMap: boolean = false;
-  @state() private disabledUnits: UnitType[] = [];
+  @state() private disabledUnits: UnitType[] = [
+    UnitType.Factory,
+    UnitType.Train,
+  ];
 
   private playersInterval: NodeJS.Timeout | null = null;
   // Add a new timer for debouncing bot changes

src/client/SinglePlayerModal.ts

@@ -40,7 +40,10 @@ export class SinglePlayerModal extends LitElement {
   @state() private gameMode: GameMode = GameMode.FFA;
   @state() private teamCount: number | typeof Duos = 2;
 
-  @state() private disabledUnits: UnitType[] = [];
+  @state() private disabledUnits: UnitType[] = [
+    UnitType.Factory,
+    UnitType.Train,
+  ];
 
   private userSettings: UserSettings = new UserSettings();
 

src/client/graphics/layers/RadialMenuElements.ts

@@ -1,3 +1,4 @@
+import { Config } from "../../../core/configuration/Config";
 import {
   AllPlayers,
   Cell,
@@ -322,6 +323,32 @@ export const infoMenuElement: MenuElement = {
   },
 };
 
+function getAllEnabledUnits(myPlayer: boolean, config: Config): Set<UnitType> {
+  const Units: Set<UnitType> = new Set<UnitType>();
+
+  const addStructureIfEnabled = (unitType: UnitType) => {
+    if (!config.isUnitDisabled(unitType)) {
+      Units.add(unitType);
+    }
+  };
+
+  if (myPlayer) {
+    addStructureIfEnabled(UnitType.City);
+    addStructureIfEnabled(UnitType.DefensePost);
+    addStructureIfEnabled(UnitType.Port);
+    addStructureIfEnabled(UnitType.MissileSilo);
+    addStructureIfEnabled(UnitType.SAMLauncher);
+    addStructureIfEnabled(UnitType.Factory);
+  } else {
+    addStructureIfEnabled(UnitType.Warship);
+    addStructureIfEnabled(UnitType.HydrogenBomb);
+    addStructureIfEnabled(UnitType.MIRV);
+    addStructureIfEnabled(UnitType.AtomBomb);
+  }
+
+  return Units;
+}
+
 export const buildMenuElement: MenuElement = {
   id: Slot.Build,
   name: "build",
@@ -332,21 +359,10 @@ export const buildMenuElement: MenuElement = {
   subMenu: (params: MenuElementParams) => {
     if (params === undefined) return [];
 
-    const unitTypes: Set<UnitType> = new Set<UnitType>();
-    if (params.selected === params.myPlayer) {
-      unitTypes.add(UnitType.City);
-      unitTypes.add(UnitType.DefensePost);
-      unitTypes.add(UnitType.Port);
-      unitTypes.add(UnitType.MissileSilo);
-      unitTypes.add(UnitType.SAMLauncher);
-      unitTypes.add(UnitType.Factory);
-    } else {
-      unitTypes.add(UnitType.Warship);
-      unitTypes.add(UnitType.HydrogenBomb);
-      unitTypes.add(UnitType.MIRV);
-      unitTypes.add(UnitType.AtomBomb);
-    }
-
+    const unitTypes: Set<UnitType> = getAllEnabledUnits(
+      params.selected === params.myPlayer,
+      params.game.config(),
+    );
     const buildElements: MenuElement[] = flattenedBuildTable
       .filter((item) => unitTypes.has(item.unitType))
       .map((item: BuildItemDisplay) => ({

src/client/graphics/layers/UnitInfoModal.ts

@@ -246,7 +246,8 @@ export class UnitInfoModal extends LitElement implements Layer {
             class="upgrade-button"
             title="${translateText("unit_info_modal.create_station")}"
             style="width: 100px; height: 32px;
-              display: ${this.unit.hasTrainStation() ||
+              display: ${this.game.config().isUnitDisabled(UnitType.Train) ||
+            this.unit.hasTrainStation() ||
             !this.game.unitInfo(this.unit.type()).canBuildTrainStation
               ? "none"
               : "block"};"

src/client/utilities/RenderUnitTypeOptions.ts

@@ -18,6 +18,8 @@ const unitOptions: { type: UnitType; translationKey: string }[] = [
   { type: UnitType.AtomBomb, translationKey: "unit_type.atom_bomb" },
   { type: UnitType.HydrogenBomb, translationKey: "unit_type.hydrogen_bomb" },
   { type: UnitType.MIRV, translationKey: "unit_type.mirv" },
+  { type: UnitType.Train, translationKey: "unit_type.train" },
+  { type: UnitType.Factory, translationKey: "unit_type.factory" },
 ];
 
 export function renderUnitTypeOptions({