repl: Add restart kernel action and improve shutdown (#16609)

- Implement restart kernel functionality
- Clean up shutdown process to properly drop messaging and exit status
tasks
- Refactor kernel state handling for better consistency

Closes #16037

Release Notes:

- repl: Added restart kernel action
- repl: Fixed issue with shutting down kernels that are in a failure
state

crates/repl/src/repl.rs

@@ -20,7 +20,7 @@ pub use crate::jupyter_settings::JupyterSettings;
 pub use crate::kernels::{Kernel, KernelSpecification, KernelStatus};
 pub use crate::repl_editor::*;
 pub use crate::repl_sessions_ui::{
-    ClearOutputs, Interrupt, ReplSessionsPage, Run, Sessions, Shutdown,
+    ClearOutputs, Interrupt, ReplSessionsPage, Restart, Run, Sessions, Shutdown,
 };
 use crate::repl_store::ReplStore;
 pub use crate::session::Session;