treewide: use dot shorthands where possible

Now this feature is stable, we should use it. I might have missed some usecases, but these can be added in future commits.

lib/widgets/renderers/generic_event.dart

@@ -7,14 +7,11 @@ class GenericEventRenderer extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) => Padding(
-    padding: EdgeInsets.only(bottom: 8),
+    padding: .only(bottom: 8),
     child: Row(
       spacing: 8,
       children: [
-        Padding(
-          padding: EdgeInsets.symmetric(horizontal: 4),
-          child: Icon(icon),
-        ),
+        Padding(padding: .symmetric(horizontal: 4), child: Icon(icon)),
         Expanded(child: Wrap(spacing: 4, children: children)),
       ],
     ),