Remove or adjust some controversial rules

[Sadhorsephile]

Problem

Some of the rules are of dubious benefit.

1.      - avoid-accessing-collections-by-constant-index

   Question is - how we'll be process such cases?

     final someString = 'some-decoded-id-in-the-middle';
     final parts = someString.split('-');
     assert(parts.length == 6, 'Incorrect format');
     return parts[2];
   }

2.        - avoid-explicit-type-declaration

   I used to avoid reduntant getter like this:

   class SomeWm extends WidgetModel<SomeWidget> {
      @override
      final ValueNotifier<int> counter = ValueNotifier(0);
   }
   
   abstract class ISomeWm extends IWidgetModel<SomeWidget> {
       ValueListenable<int> get counter;
   }

   I have to declare type explicitly. Will it work with this rule?

3.      - avoid-long-files:
              max-length: 500         

   What about situations, when we have many private widgets for one screen? They are not reusable and have to be private.

4.   - avoid-long-functions:

   Does it rule work also for build method?

[github-actions]

Link to Pyrus task

[Sadhorsephile]

1. It's okay because you can declare index variables/constants and use them::

  const indexOfId = 2;

  final someString = 'some-decoded-id-in-the-middle';
  final parts = someString.split('-');
  assert(parts.length == 6, 'Incorrect format');
  return parts[indexOfId];
}

2. We don't have this rule right now.

3. This is a rare case, in such cases it can be ignored.

4. Similar to 3.