Added torch.linalg.matrix_norm (#57127)
Summary:
This PR is focused on the API for `linalg.matrix_norm` and delegates computations to `linalg.norm` for the moment.
The main difference between the norms is when `dim=None`. In this case
- `linalg.norm` will compute a vector norm on the flattened input if `ord=None`, otherwise it requires the input to be either 1D or 2D in order to disambiguate between vector and matrix norm
- `linalg.vector_norm` will flatten the input
- `linalg.matrix_norm` will compute the norm over the last two dimensions, treating the input as batch of matrices
In future PRs, the computations will be moved to `torch.linalg.matrix_norm` and `torch.norm` and `torch.linalg.norm` will delegate computations to either `linalg.vector_norm` or `linalg.matrix_norm` based on the arguments provided.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57127
Reviewed By: mrshenli
Differential Revision: D28186736
Pulled By: mruberry
fbshipit-source-id: 99ce2da9d1c4df3d9dd82c0a312c9570da5caf25
