Migrate keymap and settings + edit predictions rename (#23834)

- [x] snake case keymap properties
- [x] flatten actions
- [x] keymap migration + notfication
- [x] settings migration + notification
- [x] inline completions -> edit predictions 

### future: 
- keymap notification doesn't show up on start up, only on keymap save.
this is existing bug in zed, will be addressed in seperate PR.

Release Notes:

- Added a notification for deprecated settings and keymaps, allowing you
to migrate them with a single click. A backup of your existing keymap
and settings will be created in your home directory.
- Modified some keymap actions and settings for consistency.

---------

Co-authored-by: Piotr Osiewicz <piotr@zed.dev>
Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>

crates/vim/src/surrounds.rs

@@ -554,11 +554,7 @@ mod test {
     use gpui::KeyBinding;
     use indoc::indoc;
 
-    use crate::{
-        state::{Mode, Operator},
-        test::VimTestContext,
-        PushOperator,
-    };
+    use crate::{state::Mode, test::VimTestContext, PushAddSurrounds};
 
     #[gpui::test]
     async fn test_add_surrounds(cx: &mut gpui::TestAppContext) {
@@ -749,7 +745,7 @@ mod test {
         cx.update(|_, cx| {
             cx.bind_keys([KeyBinding::new(
                 "shift-s",
-                PushOperator(Operator::AddSurrounds { target: None }),
+                PushAddSurrounds {},
                 Some("vim_mode == visual"),
             )])
         });