I'd like to rename and refactor the hold behavior in the Alacritty terminal codebase to better reflect its actual use and separate terminal process handling from window behavior. Please rename the hold field in all relevant config structs (Options, TerminalOptions, PtyOptions) to drain_on_exit to make it clear that the terminal should drain its output before exiting, not necessarily hold the window open. Update all associated logic and struct initializations accordingly. Additionally, add a new hold field specifically to the Window struct to control whether the terminal window should remain open after the terminal process exits. Ensure that when a user explicitly closes the window (e.g., via WindowEvent::CloseRequested), this hold flag is set to false to allow normal shutdown. Update any logic that previously depended on hold to use the appropriate new field, and include a changelog entry explaining this semantic split and why the change was made.