[UX] SkyServe terminate_replica output messages too verbose and confusing

[andylizf]

andyl@andylizf-dev-server ~/skypilot (fix-aws-name) [1]> sky serve dow
n sky-service-c4d3 --replica-id 1

Terminating replica ID 1 in 'sky-service-c4d3'. Proceed? [Y/n]: 
ValueError: Replica 1 for service sky-service-c4d3 does not exist.

sky.exceptions.CommandError: Command $([ -s ~/.sky/python_path ] && cat ~/.sky/python_path 2> /dev/null || which python3) -u -c 'from sky... failed with return code 1.
Failed to terminate the replica

The above exception was the direct cause of the following exception:

RuntimeError: Failed to terminate the replica

Expected:

andyl@andylizf-dev-server ~/skypilot (fix-aws-name) [1]> sky serve dow
n sky-service-c4d3 --replica-id 1

Terminating replica ID 1 in 'sky-service-c4d3'. Proceed? [Y/n]: 
RuntimeError: Failed to terminate the replica, since
replica 1 for service sky-service-c4d3 does not exist.

Also happens for those endpoints that use HTTP for calling functionalities remotely.