constistent classmethod and staticmethod usage

General idea is to use classmethod for every constructor and
statismethod otherwise.
Also use self and cls whenever it's possible to call static and class
methods

tests/ahriman/core/test_configuration.py

@@ -14,8 +14,8 @@ def test_from_path(mocker: MockerFixture) -> None:
     load_logging_mock = mocker.patch("ahriman.core.configuration.Configuration.load_logging")
     path = Path("path")
 
-    config = Configuration.from_path(path, "x86_64", True)
-    assert config.path == path
+    configuration = Configuration.from_path(path, "x86_64", True)
+    assert configuration.path == path
     read_mock.assert_called_with(path)
     load_includes_mock.assert_called_once()
     load_logging_mock.assert_called_once()