Let preprocessing stage becomes more popular (don't focus on scheduler)

[chenshanpei]

People want to use plugsched to extract ebpf subsystem code, and they meet lots of problems. Renaming variable, config, file from sched-prefixed name to general purpose name, will let plugsched to used in ebpf subsystem more easy.

e.g.
sched_boundary --> boundary
sched_boundary.py --> collect.py
process.py --> analyze.py
sched_boundary.yaml --> boundary.yaml