checkpoint model on first step callback (#2906)

* checkpoint model on first step callback

* remove debug

* add test cases; update existing tests not to save on first step

* move test out of solo

* delete

* default to False

* typo

tests/e2e/test_evaluate.py

@@ -36,6 +36,7 @@ class TestE2eEvaluate:
                 "optimizer": "adamw_torch_fused",
                 "lr_scheduler": "cosine",
                 "max_steps": 20,
+                "save_first_step": False,
             }
         )