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/Cargo.toml

@@ -67,6 +67,7 @@ image_viewer.workspace = true
 indoc.workspace = true
 inline_completion_button.workspace = true
 install_cli.workspace = true
+jj_ui.workspace = true
 journal.workspace = true
 language.workspace = true
 language_extension.workspace = true