python: fix bytes() on non-contiguous arrays

[axiom-of-choice]

__bytes__ reads the raw buffer pointer, which for a strided view (slice, transpose, broadcast) points into the parent array, so bytes(x[::2]) dumps neighboring memory instead of the view's values.

Make the array row-contiguous before reading, which is a no-op copy for already-packed arrays. Fixes #4445.

[simeetnayan81]

Hey, we need tests to catch these issues with calling bytes on a view. The issue was not caught earlier because test only considered packed array.

We might need these cases:
x[::2]
x[::-1]
m.T (transpose view)
m[:, 1]
broadcast_to
x[1:6] as a packed view with offset

Thanks

[simeetnayan81]

Won't this be better? We might want to save a second call if a is already packed/contiguous :

a.flags().row_contiguous ? a : mx::contiguous(a);

[zcbenz]

When a is not evaluated a.flags().row_contiguous would return garbage so we have to use mx::contiguous.

[simeetnayan81]

Oh alright. Then we may skip this. Thanks.

[zcbenz]

@axiom-of-choice Can you add a test for bytes() non-contiguous arrays?

[axiom-of-choice]

@axiom-of-choice Can you add a test for bytes() non-contiguous arrays?

@zcbenz Done!