Add benchbot to monitor and evaluate scheduling

[nolouch]

Feature Request

Describe your feature request related problem:

We do not have an effective method to measure scheduling in time.

Describe the feature you'd like:

Benchbot can run with some command after reply to some keyword in PR. we may enhance it to monitor and evaluate the impact of scheduling policy changes.

Describe alternatives you've considered:

The result may include:

• Jitter index during scheduling
• Number of redundant operators
• The time to reach the balance
• The avg compaction flow during the balance
  and so on.

Teachability, Documentation, Adoption, Migration Strategy:

such as run it with the command:

/bench-scheduler