gh-78959: Add order parameter to memoryview.cast() (GH-153663)

gh-78959: Add order parameter to memoryview.cast() (GH-153663)

memoryview.cast() now accepts a keyword-only order parameter.  With
order='F' it returns a zero-copy Fortran-contiguous (column-major) view
of a flat buffer, mirroring the order argument of memoryview.tobytes().
Only 'C' (the default) and 'F' are accepted; the buffer is not copied.