[UNTESTED] Fixes notifiers and adds some additional methods. Adds tests.

Changes:
// ArcaneEnvironment
breaking: context.read<ArcaneEnvironment>() -> ArcaneEnvironment.of(context)
breaking: context.read<ArcaneEnvironment>().state -> ArcaneEnvironment.of(context).environment;

// Feature flag service
added: reset()

// Logging service
added: registerInterface()
added: unregisterInterfaces()
added: unregisterAllInterfaces()

// ArcaneReactiveTheme
fixed: currentMode, dark, light now actually emit new values when changed
added: getters for lightTheme, darkTheme, and systemTheme
TODO: test systemTheme

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

test/arcane_test.dart

@@ -0,0 +1,22 @@
+import "package:arcane_framework/arcane_framework.dart";
+import "package:flutter_test/flutter_test.dart";
+import "package:mockito/mockito.dart";
+
+class MockLoggingInterface extends Mock implements LoggingInterface {}
+
+void main() {
+  setUpAll(() {
+    ArcaneFeatureFlags.I.reset();
+    ArcaneAuthenticationService.I.reset();
+    ArcaneReactiveTheme.I.reset();
+  });
+
+  group("Arcane", () {
+    test("services getter returns all core services", () {
+      final services = Arcane.services;
+      expect(services, contains(isA<ArcaneFeatureFlags>()));
+      expect(services, contains(isA<ArcaneAuthenticationService>()));
+      expect(services, contains(isA<ArcaneReactiveTheme>()));
+    });
+  });
+}