Prompt before quitting/reloading when terminal processes are running

[smitbarmase]

Summary

Currently we don't have way to detect if there is any process running in terminal (We only track tasks spawned by Zed itself). Once we have that, upon reloading/quitting we should prompt user for confirmation. This prompt should be same as how we prompt for unsaved buffer and onging call, i.e. ignores confirm_quit setting.