Revert "gpui: Do not render ligatures between different styled text runs (#37175) (#37382)

This reverts commit 62083fe796.

We're reverting this as it causes layout shift when typing/selecting
with ligatures:


https://github.com/user-attachments/assets/80b78909-62f5-404f-8cca-3535c5594ceb

Release Notes:

- Reverted #37175

crates/gpui/src/text_system/line_layout.rs

@@ -501,7 +501,7 @@ impl LineLayoutCache {
         } else {
             drop(current_frame);
             let text = SharedString::from(text);
-            let unwrapped_layout = self.layout_line::<&SharedString>(&text, font_size, runs, None);
+            let unwrapped_layout = self.layout_line::<&SharedString>(&text, font_size, runs);
             let wrap_boundaries = if let Some(wrap_width) = wrap_width {
                 unwrapped_layout.compute_wrap_boundaries(text.as_ref(), wrap_width, max_lines)
             } else {
@@ -535,6 +535,19 @@ impl LineLayoutCache {
         text: Text,
         font_size: Pixels,
         runs: &[FontRun],
+    ) -> Arc<LineLayout>
+    where
+        Text: AsRef<str>,
+        SharedString: From<Text>,
+    {
+        self.layout_line_internal(text, font_size, runs, None)
+    }
+
+    pub fn layout_line_internal<Text>(
+        &self,
+        text: Text,
+        font_size: Pixels,
+        runs: &[FontRun],
         force_width: Option<Pixels>,
     ) -> Arc<LineLayout>
     where