avoid_relative_lib_imports

Can't use a relative path to import a library in 'lib'.

The analyzer produces this diagnostic when the URI in an import directive has lib in the path.

Assuming that there is a file named a.dart in the lib directory:

class A {}

The following code produces this diagnostic because the import contains a path that includes lib:

import '../lib/a.dart';

Rewrite the import to not include lib in the URI:

import 'a.dart';