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/zeta/src/init.rs

@@ -5,7 +5,7 @@ use feature_flags::{
     FeatureFlagAppExt as _, PredictEditsFeatureFlag, PredictEditsRateCompletionsFeatureFlag,
 };
 use gpui::actions;
-use language::language_settings::{AllLanguageSettings, InlineCompletionProvider};
+use language::language_settings::{AllLanguageSettings, EditPredictionProvider};
 use settings::update_settings_file;
 use ui::App;
 use workspace::Workspace;
@@ -44,7 +44,7 @@ pub fn init(cx: &mut App) {
                 move |file, _| {
                     file.features
                         .get_or_insert(Default::default())
-                        .inline_completion_provider = Some(InlineCompletionProvider::None)
+                        .edit_prediction_provider = Some(EditPredictionProvider::None)
                 },
             );