[BUG] Using incx or incy with linalg::axpy results in invalid memory access

[benfred]

Describe the bug
Settingincx or incy to a value other than 1 in linalg::axpy results in invalid memory access, for the mdspan versions of lingalg::axpy

This is because the input x/y mdspan's are assumed to be c_contiguous - and having incx or incy > 1 will cause the cublasaxpy function to access memory past whats valid from the mdspan .data_handle() / .size().

Steps/Code to reproduce bug

Set incx/incy > 1 when calling linalg::axpy

Expected behavior

It seems like the incx/incy parameters shouldn't be part of the public API for the mdspan version of linalg::axpy - and maybe should be gotten from the mdspan::stride accessor (for layout_stride spans).

[cjnolet]

This is because the input x/y mdspan's are assumed to be c_contiguous

You are correct, and I think that's because the layout is not being captured in the templates here , causing only the default layout to be assumed. I think we should change this sooner rather than later (before the new API functions gets more heavy use).