* Add streaming job in LoadProc
* Add a config named desired_max_waiting_jobs
1. If the number of pending load jobs is more then desired_max_waiting_jobs, the create load stmt will be rejected.
2. If the number of need_scheduler load jobs is more then desired_max_waiting_jobs, the new routine load job will be rejected.
3. Desired max size is only a expect number, so the size of queue may be more then this number sometimes.
* Merge load manager and load jobs in jobs proc dir
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