Scheduler-Plugin: Moving and renaming function mk_sched_worker_info()

The patch contains changes for moving function 'struct sched_list_node *mk_sched_worker_info()' from src/mk_scheduler.c to src/mk_plugin.c and renames it as 'struct sched_list_node *mk_plugin_sched_get_thread_conf()', since it was found that the function is used by plugin api.