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/workspace/src/pane.rs

@@ -2928,6 +2928,6 @@ impl Render for DraggedTab {
             .selected(self.is_active)
             .child(label)
             .render(cx)
-            .font(ui_font)
+            .font_family(ui_font)
     }
 }

crates/workspace/src/workspace.rs

@@ -4004,7 +4004,7 @@ impl Render for Workspace {
             .size_full()
             .flex()
             .flex_col()
-            .font(ui_font)
+            .font_family(ui_font)
             .gap_0()
             .justify_start()
             .items_start()