refactor: fix lint issues and wire up main screen

- Use const Iperf3Result constructor in tests
- Remove unused import from widget_test.dart
- Fix unnecessary underscore warnings in Consumer builders
- Use initializing formal for iperf3Service field
- Wire up main.dart to call Iperf3BinaryPathProvider.initialize()

pubspec.yaml

@@ -31,21 +31,14 @@ dependencies:
   flutter:
     sdk: flutter
 
-  # The following adds the Cupertino Icons font to your application.
-  # Use with the CupertinoIcons class for iOS style icons.
-  cupertino_icons: ^1.0.8
+  path_provider: ^2.1.4
+  provider: ^6.1.2
 
 dev_dependencies:
+  flutter_lints: ^6.0.0
   flutter_test:
     sdk: flutter
 
-  # The "flutter_lints" package below contains a set of recommended lints to
-  # encourage good coding practices. The lint set provided by the package is
-  # activated in the `analysis_options.yaml` file located at the root of your
-  # package. See that file for information about deactivating specific lint
-  # rules and activating additional ones.
-  flutter_lints: ^6.0.0
-
 # For information on the generic Dart part of this file, see the
 # following page: https://dart.dev/tools/pub/pubspec