Compute contiguity from the actual occupied data

[sofinvalery]

Proposed changes

Compute AsStrided contiguity from the actual occupied data instead of only checking row or column contiguous layouts.

This allows dense non-row/column views, such as dense stride permutations, to be marked contiguous while keeping overlapping, gapped, broadcast-style, and negative-stride views conservative. It also computes a more accurate data_size for as_strided views.

Checklist

Put an x in the boxes that apply.

• I have read the CONTRIBUTING document
• I have run pre-commit run --all-files to format my code / installed pre-commit prior to committing changes
• I have added tests that prove my fix is effective or that my feature works
• I have updated the necessary documentation (if needed)

[zcbenz]

This looks good to me, but I'm not sure about the negative stride part. @angeloskath