Remove sched/wiki and sched/wiki2 plugins and associated code.

Remove req_node_layout, which was only used with wiki/wiki2.
This leads to removal of _get_cpu_cnt() as well.

Remove SchedulerPort, only used for communication to Moab/Maui.
Remove slurm_get_sched_port() from API.
Remove schedport from slurm_ctl_conf struct.