Enhance user input handling for llama-run (#11138)
The main motivation for this change is it was not handing
ctrl-c/ctrl-d correctly. Modify `read_user_input` to handle EOF,
"/bye" command, and empty input cases. Introduce `get_user_input`
function to manage user input loop and handle different return
cases.
Signed-off-by: Eric Curtin <ecurtin@redhat.com>
