gh-43457: Tkinter: fix design flaws in wm_attributes() (GH-111404)

* When called with a single argument to get a value, it allow to omit
  the minus prefix.
* It can be called with keyword arguments to set attributes.
* w.wm_attributes(return_python_dict=True) returns a dict instead of 
  a tuple (it will be the default in future).
* Setting wantobjects to 0 no longer affects the result.

Lib/test/test_tkinter/test_misc.py

@@ -437,6 +437,61 @@ class MiscTest(AbstractTkTest, unittest.TestCase):
         self.assertTrue(str(vi).startswith(f'{vi.major}.{vi.minor}'))
 
 
+class WmTest(AbstractTkTest, unittest.TestCase):
+
+    def test_wm_attribute(self):
+        w = self.root
+        attributes = w.wm_attributes(return_python_dict=True)
+        self.assertIsInstance(attributes, dict)
+        attributes2 = w.wm_attributes()
+        self.assertIsInstance(attributes2, tuple)
+        self.assertEqual(attributes2[::2],
+                         tuple('-' + k for k in attributes))
+        self.assertEqual(attributes2[1::2], tuple(attributes.values()))
+        # silently deprecated
+        attributes3 = w.wm_attributes(None)
+        if self.wantobjects:
+            self.assertEqual(attributes3, attributes2)
+        else:
+            self.assertIsInstance(attributes3, str)
+
+        for name in attributes:
+            self.assertEqual(w.wm_attributes(name), attributes[name])
+        # silently deprecated
+        for name in attributes:
+            self.assertEqual(w.wm_attributes('-' + name), attributes[name])
+
+        self.assertIn('alpha', attributes)
+        self.assertIn('fullscreen', attributes)
+        self.assertIn('topmost', attributes)
+        if w._windowingsystem == "win32":
+            self.assertIn('disabled', attributes)
+            self.assertIn('toolwindow', attributes)
+            self.assertIn('transparentcolor', attributes)
+        if w._windowingsystem == "aqua":
+            self.assertIn('modified', attributes)
+            self.assertIn('notify', attributes)
+            self.assertIn('titlepath', attributes)
+            self.assertIn('transparent', attributes)
+        if w._windowingsystem == "x11":
+            self.assertIn('type', attributes)
+            self.assertIn('zoomed', attributes)
+
+        w.wm_attributes(alpha=0.5)
+        self.assertEqual(w.wm_attributes('alpha'),
+                         0.5 if self.wantobjects else '0.5')
+        w.wm_attributes(alpha=1.0)
+        self.assertEqual(w.wm_attributes('alpha'),
+                         1.0 if self.wantobjects else '1.0')
+        # silently deprecated
+        w.wm_attributes('-alpha', 0.5)
+        self.assertEqual(w.wm_attributes('alpha'),
+                         0.5 if self.wantobjects else '0.5')
+        w.wm_attributes(alpha=1.0)
+        self.assertEqual(w.wm_attributes('alpha'),
+                         1.0 if self.wantobjects else '1.0')
+
+
 class BindTest(AbstractTkTest, unittest.TestCase):
 
     def setUp(self):