Remove additional wrapping elements in the chat panel (#14013)

This PR removes some wrapping elements that were used inside of the chat
panel.

To facilitate this, the `Label` component now has a `weight` method to
change the font weight.

Release Notes:

- N/A

crates/ui/src/components/label/label.rs

@@ -85,6 +85,11 @@ impl LabelCommon for Label {
         self
     }
 
+    fn weight(mut self, weight: gpui::FontWeight) -> Self {
+        self.base = self.base.weight(weight);
+        self
+    }
+
     /// Sets the line height style of the label using a [`LineHeightStyle`].
     ///
     /// # Examples