Treat static methods as class methods instead of instance methods in actors (#6756)

* Treat static methods as class methods rather than instance methods

* Add tests for static methods in actors

* Revert formatting changes

* Readd future imports

* Restructure static method check

* Documentation enhancements

* Fix linting issues

python/ray/utils.py

@@ -127,6 +127,21 @@ def is_class_method(f):
     return hasattr(f, "__self__") and f.__self__ is not None
 
 
+def is_static_method(cls, f_name):
+    """Returns whether the class has a static method with the given name.
+
+    Args:
+        cls: The Python class (i.e. object of type `type`) to
+            search for the method in.
+        f_name: The name of the method to look up in this class
+            and check whether or not it is static.
+    """
+    for cls in inspect.getmro(cls):
+        if f_name in cls.__dict__:
+            return isinstance(cls.__dict__[f_name], staticmethod)
+    return False
+
+
 def random_string():
     """Generate a random string to use as an ID.