Refactor and add new method for configuration handling

Remove redundant attribute check in __init__ method and simplify its initialization. Add a new `get` method to access configuration values more explicitly and efficiently.

tenacity/config.py

@@ -45,8 +45,7 @@ def __new__(cls):
         return cls._instance
 
     def __init__(self):
-        if not hasattr(self, '_config'):
-            self._config = {}
+        self._config = {}
 
     def set_config(self, **kwargs: t.Any) -> None:
         """Sets multiple configuration parameters."""
@@ -81,6 +80,9 @@ def get_config(self, override: t.Optional[t.Dict[str, t.Any]] = None) -> t.Dict[
     def reset_config(self):
         self._config = {}
 
+    def get(self, name: str) -> t.Any:
+        return self._config.get(name)
+
     def __getattr__(self, name: str) -> t.Any:
         return self._config.get(name)