W&B: Improve resume stability (#6611)

* log best.pt metrics at train end

* update

* Update __init__.py

* flush callbacks when using evolve

* remember batch size on resuming

* Update train.py

* improve stability of resume

Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

utils/loggers/wandb/wandb_utils.py

@@ -225,9 +225,9 @@ class WandbLogger():
             if modeldir:
                 self.weights = Path(modeldir) / "last.pt"
                 config = self.wandb_run.config
-                opt.weights, opt.save_period, opt.batch_size, opt.bbox_interval, opt.epochs, opt.hyp = str(
-                    self.weights), config.save_period, config.batch_size, config.bbox_interval, config.epochs, \
-                                                                                                       config.hyp
+                opt.weights, opt.save_period, opt.batch_size, opt.bbox_interval, opt.epochs, opt.hyp, opt.imgsz = str(
+                    self.weights), config.save_period, config.batch_size, config.bbox_interval, config.epochs,\
+                    config.hyp, config.imgsz
         data_dict = self.data_dict
         if self.val_artifact is None:  # If --upload_dataset is set, use the existing artifact, don't download
             self.train_artifact_path, self.train_artifact = self.download_dataset_artifact(data_dict.get('train'),