don't initialize cuda at import time (#3244)

Author: technillogue

py/torch_tensorrt/ts/_compile_spec.py

@@ -307,7 +307,7 @@ def _parse_compile_spec(compile_spec_: Dict[str, Any]) -> _ts_C.CompileSpec:
 def TensorRTCompileSpec(
     inputs: Optional[List[torch.Tensor | Input]] = None,
     input_signature: Optional[Any] = None,
-    device: torch.device | Device = Device._current_device(),
+    device: Optional[torch.device | Device] = None,
     disable_tf32: bool = False,
     sparse_weights: bool = False,
     enabled_precisions: Optional[Set[torch.dtype | dtype]] = None,
@@ -365,7 +365,7 @@ def TensorRTCompileSpec(
     compile_spec = {
         "inputs": inputs if inputs is not None else [],
         # "input_signature": input_signature,
-        "device": device,
+        "device": Device._current_device() if device is None else device,
         "disable_tf32": disable_tf32,  # Force FP32 layers to use traditional as FP32 format vs the default behavior of rounding the inputs to 10-bit mantissas before multiplying, but accumulates the sum using 23-bit mantissas
         "sparse_weights": sparse_weights,  # Enable sparsity for convolution and fully connected layers.
         "enabled_precisions": (