Mock implementation part 2

[CalvinNeo]

What problem does this PR solve?

1. Add support for AdminCmds with consistency checking
2. Make several integration tests compactible
3. Fix several unstable test cases
4. Add support for grcov
5. Add some new tests such as read batch index

What is not included in this PR:

1. Try to return NotFound in several cases
2. Make applying raft write commands async

Problem Summary:

What is changed and how it works?

Proposal: xxx

What's Changed:

Related changes

• PR to update pingcap/docs/pingcap/docs-cn:
• PR to update pingcap/tidb-ansible:
• Need to cherry-pick to the release branch

Check List

Tests

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

Side effects

• Performance regression
  • Consumes more CPU
  • Consumes more MEM
• Breaking backward compatibility

Release note

Support more test cases and enhance stability of all test cases

[solotzg]

Can we reutrn Persist directly ?

[CalvinNeo]

I find in tiflash, apply state persistence can be skipped, when the snapshot is empty. So I think I should also mock this behavior.

[solotzg]

Before pingcap/tiflash#1811, BR/Lightning may let ingest sst cmd contain only one CF. It may cause that tiflash can not flush all region cache into column storage and region->dataSize() will be bigger than 0. After write&default cf sst ingested, tiflash can flush all and region->dataSize() will be 0.