Improved torch.einsum testing and fixed bug (#59731)
Summary:
Improved torch.einsum testing and fixed a bug where lower case letters appeared before upper case letters in the sorted order which is inconsistent with NumPy.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/59731
Reviewed By: SplitInfinity, ansley
Differential Revision: D29183078
Pulled By: heitorschueroff
fbshipit-source-id: a33980d273707da2d60a387a2af2fa41527ddb68
