fix: Repair import error for legacy TS testing (#2091)

Author: gs-olive

py/torch_tensorrt/dynamo/__init__.py

@@ -1,2 +1,6 @@
-from torch_tensorrt.dynamo import fx_ts_compat
-from .backend import compile
+import torch
+from packaging import version
+
+if version.parse(torch.__version__) >= version.parse("2.1.dev"):
+    from torch_tensorrt.dynamo import fx_ts_compat
+    from .backend import compile

py/torch_tensorrt/fx/tracer/dispatch_tracer/aten_tracer.py

@@ -2,10 +2,11 @@
 import sys
 from contextlib import contextmanager
 from typing import Any, Callable, Dict, Generator, List, Optional, Set, Tuple, Union
+from packaging import version
 
 import torch
 
-if not torch.__version__.startswith("1"):
+if version.parse(torch.__version__) >= version.parse("2.dev"):
     import torch._dynamo as torchdynamo
 
 from torch.fx.passes.infra.pass_base import PassResult