Refactor diag thread to have full control over the QMDL store

Fixes #269. Refactor also pull diag thread logic out into state machine
object for better encapsulation and reuse.

daemon/src/main.rs

@@ -229,6 +229,7 @@ async fn run_with_config(
             &task_tracker,
             dev,
             diag_rx,
+            diag_tx.clone(),
             ui_update_tx.clone(),
             qmdl_store_lock.clone(),
             analysis_tx.clone(),
@@ -284,7 +285,6 @@ async fn run_with_config(
         config,
         qmdl_store_lock: qmdl_store_lock.clone(),
         diag_device_ctrl_sender: diag_tx,
-        ui_update_sender: ui_update_tx,
         analysis_status_lock,
         analysis_sender: analysis_tx,
         daemon_restart_tx: Arc::new(RwLock::new(Some(daemon_restart_tx))),