MAINT: linalg.hankel: warn against changing behavior for multidimensional arrays

Hi team,

Like linalg.toeplitz, linalg.solve_toeplitz, and linalg.matmul_toeplitz did, linalg.hankel currently documents that c and r with dimensionality greater than 1 will be raveled.

gh-21446 and gh-22193 added warnings that the toeplitz functions would no longer ravel in SciPy 1.17; rather, multidimensional arrays would be treated as batches of 1-D arrays.

gh-23680 proposed to add a similar warning to linalg.hankel so batch support can be added in SciPy 1.19.

Please consider joining the discussion in gh-23680.

Thanks,
Matt