Extract title_bar crate (#13597)

This PR extracts a singular title bar (`title_bar::TitleBar`) from
`ui::TitleBar` and
`collab_ui::collab_titlebar_item::CollabTitlebarItem`.

This is a first step towards organizing title bar things into one place,
and standardizing platform titlebar/window control implementations.

Release Notes:

- N/A

crates/ui/src/components.rs

@@ -5,6 +5,7 @@ mod context_menu;
 mod disclosure;
 mod divider;
 mod dropdown_menu;
+mod facepile;
 mod icon;
 mod indicator;
 mod keybinding;
@@ -19,7 +20,6 @@ mod setting;
 mod stack;
 mod tab;
 mod tab_bar;
-mod title_bar;
 mod tool_strip;
 mod tooltip;
 
@@ -33,6 +33,7 @@ pub use context_menu::*;
 pub use disclosure::*;
 pub use divider::*;
 use dropdown_menu::*;
+pub use facepile::*;
 pub use icon::*;
 pub use indicator::*;
 pub use keybinding::*;
@@ -47,7 +48,6 @@ pub use setting::*;
 pub use stack::*;
 pub use tab::*;
 pub use tab_bar::*;
-pub use title_bar::*;
 pub use tool_strip::*;
 pub use tooltip::*;