Provide option for "Restart the REPL" in REPL status bar menu

[lspector]

Currently one can restart the REPL in a couple of ways, but it would be helpful to have a more straightforward way to do it, particularly for beginners.

Behind some of the current methods there is a bit of confusing terminology (e.g. because "Disconnect" also kills but only if the REPL was started by Calva) and some things only work in specific contexts (like command keys that will kill the REPL but only with the right pane in focus). The simplest option seems to be to jack-in again, which kills the old REPL and gives you a new one, which is often what is really wanted. However, if the way the user ordinarily jacks in is to use the REPL ⚡ button in the status bar, then that won't currently work because the menu won't have a "jack-in" option when the old REPL is still running.

In light of this, the suggestion is to add a "Restart the REPL" option in the menu behind the REPL ⚡ button in the status bar.