vim: Rename wrapping keybindings + document cursor wrapping (#25694)

https://github.com/zed-industries/zed/pull/25663#issuecomment-2686095807

Renamed the `vim::Backspace` and `vim::Space` actions to
`vim::WrappingLeft` and `vim::WrappingRight` respectively. The old names
are still available, but they are marked as deprecated and users are
advised to use the new names.

Also added a paragraph to the docs describing how to enable wrapping
cursor navigation.