trunk/7a192a61c9e27f379e1b5492be6f152b76be7609: Replace __args__ with typing.get_args() and TensorType.dims (#183006)

Addresses #169073. Two changes:

1. 
   

   TensorType (torch/fx/tensor_type.py) was using args and origin
   
   to mimic a typing generic, but it's actually a domain type representing
   
   tensor dimensions. Added a dims property and migrated all internal
   
   usages from .__args__ to .dims (the backing __args__ attribute
   
   is kept for backward compat). This removes the confusion about whether
   
   TensorType should be accessed via typing.get_args().

   
   


2. 
   

   Replaced all remaining .__args__ accesses on standard typing generics
   
   (Union, List, Tuple, etc.) with typing.get_args(), the recommended
   
   public API. Covers operator_schemas, graph codegen, dynamo variables,
   
   inductor fuzzer, datapipes typing, and several other modules.

   
   

Authored with Claude.

Pull Request resolved: #183006

Approved by: https://github.com/Skylion007