Fine-tuning the @typescript-eslint/no-unused-vars rule

We now allow parameters to be unused. This is quite common in inherited methods.
This allows removing a bunch of: //eslint-disable-next-line @typescript-eslint/no-unused-vars
Also, "err" variables in catch MUST now be used and the special _exhaustiveCheck variable used in ":never" assigns can be unused.

back/src/Model/Zone.ts

@@ -71,7 +71,6 @@ export class Zone {
     /**
      * Notify listeners of this zone that this user entered
      */
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
     private notifyEnter(thing: Movable, oldZone: Zone | null, position: PositionInterface) {
         for (const listener of this.listeners) {
             this.onEnters(thing, oldZone, listener);

back/src/Services/Repository/VoidVariablesRepository.ts

@@ -4,12 +4,10 @@ import { VariablesRepositoryInterface } from "./VariablesRepositoryInterface";
  * Mock class in charge of NOT saving/loading variables from the data store
  */
 export class VoidVariablesRepository implements VariablesRepositoryInterface {
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
     loadVariables(roomUrl: string): Promise<{ [key: string]: string }> {
         return Promise.resolve({});
     }
 
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
     saveVariable(roomUrl: string, key: string, value: string): Promise<number> {
         return Promise.resolve(0);
     }