Reland "Remove cx from ThemeSettings" (#39720)

- **Reapply "Remove cx from ThemeSettings (#38836)" (#39691)**
- **Fix theme loading races**

Closes #ISSUE

Release Notes:

- N/A

crates/vim_mode_setting/src/vim_mode_setting.rs

@@ -16,7 +16,7 @@ pub fn init(cx: &mut App) {
 pub struct VimModeSetting(pub bool);
 
 impl Settings for VimModeSetting {
-    fn from_settings(content: &SettingsContent, _cx: &mut App) -> Self {
+    fn from_settings(content: &SettingsContent) -> Self {
         Self(content.vim_mode.unwrap())
     }
 
@@ -28,7 +28,7 @@ impl Settings for VimModeSetting {
 pub struct HelixModeSetting(pub bool);
 
 impl Settings for HelixModeSetting {
-    fn from_settings(content: &SettingsContent, _cx: &mut App) -> Self {
+    fn from_settings(content: &SettingsContent) -> Self {
         Self(content.helix_mode.unwrap())
     }