WIP: add axis tuple support to torch.expand_dims

[ev-br]

1. update for default axis (the argument is required)
2. copycat what numpy does for the tuple axes
3. TODO check the defaults for other wrappers (numpy,cupy,dask) seems fine

Draft until 2025.12 is a thing and includes data-apis/array-api#988

[Copilot]

Pull request overview

This PR adds support for tuple values in the axis parameter of torch.expand_dims, allowing multiple dimensions to be expanded at once. This aligns with the Array API 2024.12 standard.

Changes:

• Extended expand_dims function signature to accept axis: int | tuple[int, ...] instead of just axis: int
• Added implementation logic to handle tuple axes by computing the expected output shape and using torch.reshape
• Added validation for duplicate axes and out-of-range axis values

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