serial: improve robustness when trying to stop or restart serial

Do not abort if serial cannot be restarted, and improve when the
serial-enabled flag is set so that it indicates the tasks are running
so that trying to stop serial does not wait for tasks to exit that have
not been started and are not actually running.

main/serial.c

@@ -284,6 +284,9 @@ static bool serial_init_internal(void)
     }
 #endif // IDF_TARGET_ESP32
 
+    // The tasks run while this flag is set
+    serial_is_enabled = true;
+
     BaseType_t retval = xTaskCreatePinnedToCore(&serial_reader, "serial_reader", reader_stack_size, NULL,
         JADE_TASK_PRIO_READER, &serial_reader_handle, JADE_CORE_SECONDARY);
 
@@ -294,6 +297,7 @@ static bool serial_init_internal(void)
         p_serial_writer_handle, JADE_CORE_SECONDARY);
     JADE_ASSERT_MSG(
         retval == pdPASS, "Failed to create serial_writer task, xTaskCreatePinnedToCore() returned %d", retval);
+
     return true;
 }
 
@@ -315,29 +319,25 @@ bool serial_init(TaskHandle_t* serial_handle)
     full_serial_data_in[0] = SOURCE_SERIAL;
     serial_data_out = JADE_MALLOC_PREFER_SPIRAM(MAX_OUTPUT_MSG_SIZE);
     p_serial_writer_handle = serial_handle;
-    serial_is_enabled = true;
     return serial_init_internal();
 }
 
 bool serial_enabled(void) { return serial_is_enabled; }
 
 void serial_start(void)
 {
-    // JADE_ASSERT(!serial_is_enabled);
     if (serial_is_enabled) {
         return;
     }
-    serial_is_enabled = true;
-    const bool res = serial_init_internal();
-    JADE_ASSERT(res);
+    serial_init_internal();
 }
 
 void serial_stop(void)
 {
-    // JADE_ASSERT(serial_is_enabled);
     if (!serial_is_enabled) {
         return;
     }
+
     // flag tasks to die
     serial_is_enabled = false;