refactor: Use error!(e; xxx) pattern to log error (#195)

Use `error!(e; xxx)` pattern so we could get backtrace in error log.

Also use BoxedError as error source of ExecuteQuery instead of String,
so we could carry backtrace and other info in it.

src/storage/src/region/writer.rs

@@ -359,11 +359,7 @@ impl WriterInner {
             // TODO(yingwen): We should release the write lock during waiting flush done, which
             // needs something like async condvar.
             flush_handle.join().await.map_err(|e| {
-                logging::error!(
-                    "Previous flush job failed, region: {}, err: {}",
-                    shared.name,
-                    e
-                );
+                logging::error!(e; "Previous flush job failed, region: {}", shared.name);
                 e
             })?;
         }