New revision of the Assistant Panel (#10870)

This is a crate only addition of a new version of the AssistantPanel.
We'll be putting this behind a feature flag while we iron out the new
experience.

Release Notes:

- N/A

---------

Co-authored-by: Nathan Sobo <nathan@zed.dev>
Co-authored-by: Antonio Scandurra <me@as-cii.com>
Co-authored-by: Conrad Irwin <conrad@zed.dev>
Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>
Co-authored-by: Antonio Scandurra <antonio@zed.dev>
Co-authored-by: Nate Butler <nate@zed.dev>
Co-authored-by: Nate Butler <iamnbutler@gmail.com>
Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>
Co-authored-by: Max <max@zed.dev>

crates/assistant2/src/assistant_settings.rs

@@ -0,0 +1,26 @@
+use schemars::JsonSchema;
+use serde::{Deserialize, Serialize};
+use settings::{Settings, SettingsSources};
+
+#[derive(Default, Debug, Deserialize, Serialize, Clone)]
+pub struct AssistantSettings {
+    pub enabled: bool,
+}
+
+#[derive(Default, Debug, Deserialize, Serialize, Clone, JsonSchema)]
+pub struct AssistantSettingsContent {
+    pub enabled: Option<bool>,
+}
+
+impl Settings for AssistantSettings {
+    const KEY: Option<&'static str> = Some("assistant_v2");
+
+    type FileContent = AssistantSettingsContent;
+
+    fn load(
+        sources: SettingsSources<Self::FileContent>,
+        _: &mut gpui::AppContext,
+    ) -> anyhow::Result<Self> {
+        Ok(sources.json_merge().unwrap_or_else(|_| Default::default()))
+    }
+}