Merge Component and ComponentPreview trait (#28365)

- Merge `Component` and `ComponentPreview` trait
- Adds a number of component previews
- Removes a number of stories

Release Notes:

- N/A

crates/ui/src/component_prelude.rs

@@ -0,0 +1,5 @@
+pub use component::{
+    Component, ComponentScope, example_group, example_group_with_title, single_example,
+};
+pub use documented::Documented;
+pub use ui_macros::RegisterComponent;