Massively simplify API binding logic

Changes the API internals to use normal Laravel binding which automatically supports nested-models and can determine their relationships. This removes a lot of confusingly complex internal logic and replaces it with standard Laravel code.

This also removes a deprecated "getModel" method and fully replaces it with a "parameter" method that does stricter type-checking.

app/Http/Requests/Api/Application/Locations/UpdateLocationRequest.php

@@ -6,16 +6,6 @@ use Pterodactyl\Models\Location;
 
 class UpdateLocationRequest extends StoreLocationRequest
 {
-    /**
-     * Determine if the requested location exists on the Panel.
-     */
-    public function resourceExists(): bool
-    {
-        $location = $this->route()->parameter('location');
-
-        return $location instanceof Location && $location->exists;
-    }
-
     /**
      * Rules to validate this request against.
      */