Use latest packet timestamp in GPS file, move writing into DiagTask to eliminate RwLocks, remove "sidecar" word from codebase

lib/src/diag_device.rs

@@ -212,7 +212,7 @@ impl DiagDevice {
             if container.data_type != DataType::UserSpace {
                 continue;
             }
-            return Ok(container.into_messages());
+            return Ok(container.messages());
         }
     }