model: Move random seed and random to __init__

Given that `super().__init__()` is now necessary for user's model class `__init__()`, this simplifies the `Model` construct.
And  `model.random` can be initialized with other RNG objects (`np.random.default_rng(...)`, or any other RNG).

Prior discussion #1938 Please enter the commit message for your changes. Lines starting

mesa/model.py

@@ -49,20 +49,6 @@ class Model:
         initialize_data_collector: Sets up the data collector for the model, requiring an initialized scheduler and agents.
     """
 
-    def __new__(cls, *args: Any, **kwargs: Any) -> Any:
-        """Create a new model object and instantiate its RNG automatically."""
-        obj = object.__new__(cls)
-        obj._seed = kwargs.get("seed")
-        if obj._seed is None:
-            # We explicitly specify the seed here so that we know its value in
-            # advance.
-            obj._seed = random.random()
-        obj.random = random.Random(obj._seed)
-        # TODO: Remove these 2 lines just before Mesa 3.0
-        obj._steps = 0
-        obj._time = 0
-        return obj
-
     def __init__(self, *args: Any, **kwargs: Any) -> None:
         """Create a new model. Overload this method with the actual code to
         start the model. Always start with super().__init__() to initialize the
@@ -74,6 +60,13 @@ def __init__(self, *args: Any, **kwargs: Any) -> None:
         self.current_id = 0
         self.agents_: defaultdict[type, dict] = defaultdict(dict)
 
+        self._seed = kwargs.get("seed")
+        if self._seed is None:
+            # We explicitly specify the seed here so that we know its value in
+            # advance.
+            self._seed = random.random()
+        self.random = random.Random(self._seed)
+
         self._steps: int = 0
         self._time: TimeT = 0  # the model's clock