LWG-3848 `adjacent_view`, `adjacent_transform_view`, and `slide_view` missing `base` accessor

LWG-3848 `adjacent_view`, `adjacent_transform_view`, and `slide_view` missing `base` accessor

`slide_view` needs to be patched.

`adjacent_view` and `adjacent_transform_view` are not yet implemented; I've recorded this issue in #2252.