fix(tui): generate stop event on ctrl c (#9296)
### Description
Previously we had used a `None` return from the input handler as a
signal that the TUI should shut down. We no longer do this so we need to
explicitly return `Event::InternalStop` to signal that we should shut
down the TUI.
### Testing Instructions
Start up a dev task with 2.2.1 and observe that on Ctrl-C the terminal
is left in raw mode:
<img width="1074" alt="Screenshot 2024-10-20 at 3 31 40 PM"
src="https://github.com/user-attachments/assets/9b8abf85-20b6-4991-aa64-09a1edcc617b">
With the build from the PR you should note that the on Ctrl-C the
terminal is returned to a cooked mode:
<img width="582" alt="Screenshot 2024-10-20 at 3 32 14 PM"
src="https://github.com/user-attachments/assets/521381d6-6a28-4dbb-b56b-0d1cae7fbd27">
