Add row & bytes threshold config for CompactLog (#1997)

[ti-srebot]

cherry-pick #1997 to release-4.0
You can switch your code base to this Pull Request by using git-extras:

# In tics repo:
git pr https://github.com/pingcap/tics/pull/2004

After apply modifications, you can push your change to this PR via:

git push [email protected]:ti-srebot/tics.git pr/2004:release-4.0-558787749f42

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Signed-off-by: Zhigao Tong [email protected]

What problem does this PR solve?

Issue Number: close #1885

Problem Summary:

What is changed and how it works?

What's Changed:

• add config about rows & bytes threshold for compact log.
• if mem cache about one region reach any threshold( rows: 40k | bytes: 32MB | period: 120), its cache should be flushed and persisted.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Release note

• No release note

[solotzg]

/merge

[ti-srebot]

/run-all-tests