Add a picker for jj bookmark list (#30883)

This PR adds a new picker for viewing a list of jj bookmarks, like you
would with `jj bookmark list`.

This is an exploration around what it would look like to begin adding
some dedicated jj features to Zed.

This is behind the `jj-ui` feature flag.

Release Notes:

- N/A

crates/zed_actions/src/lib.rs

@@ -142,6 +142,12 @@ pub mod git {
     action_with_deprecated_aliases!(git, Branch, ["branches::OpenRecent"]);
 }
 
+pub mod jj {
+    use gpui::actions;
+
+    actions!(jj, [BookmarkList]);
+}
+
 pub mod command_palette {
     use gpui::actions;