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>

docs/src/configuring-zed.md

@@ -378,11 +378,11 @@ There are two options to choose from:
 ## Edit Predictions
 
 - Description: Settings for edit predictions.
-- Setting: `inline_completions`
+- Setting: `edit_predictions`
 - Default:
 
 ```json
-  "inline_completions": {
+  "edit_predictions": {
     "disabled_globs": [
       "**/.env*",
       "**/*.pem",
@@ -409,7 +409,7 @@ List of `string` values
 ## Edit Predictions Disabled in
 
 - Description: A list of language scopes in which edit predictions should be disabled.
-- Setting: `inline_completions_disabled_in`
+- Setting: `edit_predictions_disabled_in`
 - Default: `[]`
 
 **Options**
@@ -434,7 +434,7 @@ List of `string` values
 {
   "languages": {
     "Go": {
-      "inline_completions_disabled_in": ["comment", "string"]
+      "edit_predictions_disabled_in": ["comment", "string"]
     }
   }
 }
@@ -1478,7 +1478,7 @@ The following settings can be overridden for each specific language:
 - [`hard_tabs`](#hard-tabs)
 - [`preferred_line_length`](#preferred-line-length)
 - [`remove_trailing_whitespace_on_save`](#remove-trailing-whitespace-on-save)
-- [`show_inline_completions`](#show-inline-completions)
+- [`show_edit_predictions`](#show-edit-predictions)
 - [`show_whitespaces`](#show-whitespaces)
 - [`soft_wrap`](#soft-wrap)
 - [`tab_size`](#tab-size)
@@ -1654,8 +1654,8 @@ Or to set a `socks5` proxy:
 
 ## Show Edit Predictions
 
-- Description: Whether to show edit predictions as you type or manually by triggering `editor::ShowInlineCompletion`.
-- Setting: `show_inline_completions`
+- Description: Whether to show edit predictions as you type or manually by triggering `editor::ShowEditPrediction`.
+- Setting: `show_edit_predictions`
 - Default: `true`
 
 **Options**