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.

assets/keymaps/vim.json

@@ -6,7 +6,7 @@
       "a": ["vim::PushObject", { "around": true }],
       "left": "vim::Left",
       "h": "vim::Left",
-      "backspace": "vim::Backspace",
+      "backspace": "vim::WrappingLeft",
       "down": "vim::Down",
       "ctrl-j": "vim::Down",
       "j": "vim::Down",
@@ -20,7 +20,7 @@
       "k": "vim::Up",
       "right": "vim::Right",
       "l": "vim::Right",
-      "space": "vim::Space",
+      "space": "vim::WrappingRight",
       "end": "vim::EndOfLine",
       "$": "vim::EndOfLine",
       "^": "vim::FirstNonWhitespace",