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/supermaven/src/supermaven_completion_provider.rs

@@ -2,7 +2,7 @@ use crate::{Supermaven, SupermavenCompletionStateId};
 use anyhow::Result;
 use futures::StreamExt as _;
 use gpui::{App, Context, Entity, EntityId, Task};
-use inline_completion::{Direction, InlineCompletion, InlineCompletionProvider};
+use inline_completion::{Direction, EditPredictionProvider, InlineCompletion};
 use language::{Anchor, Buffer, BufferSnapshot};
 use project::Project;
 use std::{
@@ -97,7 +97,7 @@ fn completion_from_diff(
     }
 }
 
-impl InlineCompletionProvider for SupermavenCompletionProvider {
+impl EditPredictionProvider for SupermavenCompletionProvider {
     fn name() -> &'static str {
         "supermaven"
     }