Separate the concepts of archived and disconnected devices

Summary:
Minor code cleanup to avoid future confusion:

- archived: a device that was imported from a Flipper trace, and only has persisted state
- (dis)connected: a real stateful device that might or might not have an active connection

Reviewed By: nikoant

Differential Revision: D26275459

fbshipit-source-id: eba554b37c39711e367c3795ff4456329a303c22

desktop/flipper-plugin/src/test-utils/test-utils.tsx

@@ -421,6 +421,7 @@ function createMockDevice(options?: StartPluginOptions): RealFlipperDevice {
     deviceType: 'emulator',
     serial: 'serial-000',
     isArchived: !!options?.isArchived,
+    connected: createState(true),
     devicePlugins: [],
     addLogListener(cb) {
       logListeners.push(cb);