Allow to hide more buttons with the settings (#30565)

* project search button in the status bar
```jsonc
"search": {
  "button": false
},
```

* project diagnostics button in the status bar
```jsonc
"diagnostics": {
  "button": false
}
```

* project name and host buttons in the title bar
```jsonc
"title_bar": {
    "show_project_items": false
}
```

* git branch button in the title bar
```jsonc
"title_bar": {
    "show_branch_name": false
}
```

Before:
<img width="1728" alt="before"
src="https://github.com/user-attachments/assets/4b13b431-3ac1-43b3-8ac7-469e5a9ccf7e"
/>

After:
<img width="1728" alt="after"
src="https://github.com/user-attachments/assets/baf2765a-e27b-47a3-8897-89152b7a7c95"
/>


Release Notes:

- Added more settings to hide buttons from Zed UI

crates/project/src/project_settings.rs

@@ -119,11 +119,15 @@ pub enum DirenvSettings {
 
 #[derive(Clone, Debug, Default, Serialize, Deserialize, JsonSchema)]
 pub struct DiagnosticsSettings {
-    /// Whether or not to include warning diagnostics
-    #[serde(default = "true_value")]
+    /// Whether to show the project diagnostics button in the status bar.
+    #[serde(default = "default_true")]
+    pub button: bool,
+
+    /// Whether or not to include warning diagnostics.
+    #[serde(default = "default_true")]
     pub include_warnings: bool,
 
-    /// Settings for showing inline diagnostics
+    /// Settings for showing inline diagnostics.
     #[serde(default)]
     pub inline: InlineDiagnosticsSettings,
 
@@ -304,7 +308,7 @@ pub struct InlineBlameSettings {
     /// the currently focused line.
     ///
     /// Default: true
-    #[serde(default = "true_value")]
+    #[serde(default = "default_true")]
     pub enabled: bool,
     /// Whether to only show the inline blame information
     /// after a delay once the cursor stops moving.
@@ -322,10 +326,6 @@ pub struct InlineBlameSettings {
     pub show_commit_summary: bool,
 }
 
-const fn true_value() -> bool {
-    true
-}
-
 #[derive(Clone, Debug, Default, Serialize, Deserialize, PartialEq, Eq, JsonSchema)]
 pub struct BinarySettings {
     pub path: Option<String>,