reparo/:Add worker-count, txn-batch config (#742)

[lichunzhu]

What problem does this PR solve?

cherry-pick #742
TOOL-1547
Add worker count and txn batch config for reparo. Users can decide these indecies themselves to change the sync speed of reparo.

What is changed and how it works?

Expose worker count and txn batch to config.

Check List

Tests

• Unit test
• Integration test

Code changes

Side effects

Related changes

• Need to update the documentation
• Need to be included in the release note

[lichunzhu]

/run-all-tests

[july2993]

LGTM

[WangXiangUSTC]

LGTM

[huynhphuong10284]

Just ask a question about "txn-batch" (default = 20) as below:

• If my system is big data, it has an issue that data will be delayed for a long time.
• If my system is small data, this value may be impacted to data delays.

The concern is "how to define a good value for any case in my system?"

[lichunzhu]

@huynhphuong10284 It's not easy to "define a good value for any case in my system". For most of the time the default setting is enough. If you found that the latency is too high you can try increasing worker-count. If it doesn't work you can ask help from us.