Introduce settings profiles (#35339)

Settings Profiles

- [X] Allow profiles to be defined, where each profile can be any of
Zed's settings
    - [X] Autocompletion of all settings
    - [X] Errors on invalid keys
- [X] Action brings up modal that shows user-defined profiles
- [X] Alphabetize profiles
- [X] Ability to filter down via keyboard, and navigate via arrow up and
down
- [X] Auto select Disabled option by default (first in list, after
alphabetizing user-defined profiles)
- [X] Automatically select active profile on next picker summoning
- [X] Persist settings until toggled off
- [X] Show live preview as you select from the profile picker
- [X] Tweaking a setting, while in a profile, updates the profile live
- [X] Make sure actions that live update Zed, such as `cmd-0`, `cmd-+`,
and `cmd--`, work while in a profile
- [X] Add a test to track state

Release Notes:

- Added the ability to configure settings profiles, via the "profiles"
key. Example:

```json
{
  "profiles": {
    "Streaming": {
      "agent_font_size": 20,
      "buffer_font_size": 20,
      "theme": "One Light",
      "ui_font_size": 20
    }
  }
}
```

To set a profile, use `settings profile selector: toggle`

crates/zed_actions/src/lib.rs

@@ -260,6 +260,16 @@ pub mod icon_theme_selector {
     }
 }
 
+pub mod settings_profile_selector {
+    use gpui::Action;
+    use schemars::JsonSchema;
+    use serde::Deserialize;
+
+    #[derive(PartialEq, Clone, Default, Debug, Deserialize, JsonSchema, Action)]
+    #[action(namespace = settings_profile_selector)]
+    pub struct Toggle;
+}
+
 pub mod agent {
     use gpui::actions;