fix(templates): icon-only buttons, selects and delete pages have accessible names

An accessibility scan (axe-core, WCAG 2 A/AA) of every page found 87
elements without a name. Icon-only buttons and links (the navbar's
administration menu on every page, the add/create buttons, the flavor
delete and back buttons) get a title, which is also their tooltip; the
labels of the language, architecture, chipset and filter selects point
at them; the memory bar is named. The shared delete confirmation page
had an empty <title> and heading, as no view passes "title": it says
"Delete <object>". The power-off form's aria-label was misspelled.

admin/tests/test_views.py

@@ -39,6 +39,8 @@ class AdminTestCase(TestCase):
 
         response = self.client.get(reverse("admin:group_delete", args=[group_id]))
         self.assertEqual(response.status_code, 200)
+        # the shared confirmation page names what it deletes
+        self.assertContains(response, "<title>Delete Updated Group Test</title>", html=True)
 
         response = self.client.post(reverse("admin:group_delete", args=[group_id]))
         self.assertRedirects(response, reverse("admin:group_list"))