Add tf independent serialization (#5308)
Create a serialization format for StableHLO graphs and weights without tf.saved_model
Need to not use tensorflow because tensorflow is no longer dependency of pytorch/xla.
Information saved are enough to reconstruct the tf.saved_model for serving.
Information stored:
* metadata on which tensor maps which input position
* StableHLO version number
* metadata on which tensor corresponds to user input or parameter
* metadata on shape and dtype of each tensor.
* Tensors themselves are saved as numpy arrays using np.save.
