editor: Add active match highlight for buffer and project search (#44098)

Closes #28617

<img width="400" alt="image"
src="https://github.com/user-attachments/assets/b1c2880c-5744-4bed-a687-5c5e7aa7fef5"
/>

Release Notes:

- Improved visibility of the currently active match when browsing
results in buffer or project search.

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Co-authored-by: DarkMatter-999 <darkmatter999official@gmail.com>

crates/settings/src/settings_content/theme.rs

@@ -570,6 +570,9 @@ pub struct ThemeColorsContent {
     #[serde(rename = "search.match_background")]
     pub search_match_background: Option<String>,
 
+    #[serde(rename = "search.active_match_background")]
+    pub search_active_match_background: Option<String>,
+
     #[serde(rename = "panel.background")]
     pub panel_background: Option<String>,