Make client -> device connection synchronous

Summary:
devices not always being readily available is causes a lot of complication in the api,
figured to resolve devices first before construction clients,
since clients not attached to a device are shown uncategorized anyway, making them practically un-interactable.
For more background info, see following chat.

{F344388883}

This diff will make it possible to only expose a synchronous api in Sandy

n.b. didn't update Navigation plugin, as that is done in a next diff

Reviewed By: jknoxville

Differential Revision: D24858332

fbshipit-source-id: 8339f831fbbc9c219add56a199364fde67adafc7

desktop/app/src/plugin.tsx

@@ -285,10 +285,17 @@ export class FlipperPlugin<
   client: PluginClient;
   realClient: Client;
 
+  /**
+   * @deprecated use .device instead
+   */
   getDevice(): Promise<BaseDevice> {
     return this.realClient.device;
   }
 
+  get device() {
+    return this.realClient.deviceSync;
+  }
+
   _teardown() {
     // automatically unsubscribe subscriptions
     const pluginId = this.constructor.id;