Refactor TiFlashRaftConfig / Define main entry point for gtests_dbms (#1583)

[ti-srebot]

cherry-pick #1583 to release-5.0
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/1585

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

git push [email protected]:ti-srebot/tics.git pr/1585:release-5.0-8f0b7ef1ea94

---

Signed-off-by: JaySon-Huang [email protected]

What problem does this PR solve?

This PR is extracted from #1439 for making it easier to review. This PR mainly refactor the TiFlashRaftConfig

What is changed and how it works?

• Refactor RaftConfig to make it more tidy
• Define main entry point for gtests_dbms to
  • Not making our gtests_dbms invalid like this gtests_dbms doesn't include Function tests #1539 (comment)
  • Make initializing GlobalContext/Logger for gtests_dbms more clear

Related changes

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

Check List

Tests

• Unit test

Side effects

• N/A

Release note

• No release note

[JaySon-Huang]

cherry-pick #1593

[JaySon-Huang]

/run-all-tests