domain: move async load stats into single goroutine (#58302)

[ti-chi-bot]

This is an automated cherry-pick of #58302

What problem does this PR solve?

Issue Number: close #58303

Problem Summary:

What changed and how does it work?

Now async load and sync stats are put together, so if sync stats takes too long, it will affect async load. Although there should be no async load after sync load is turned on, from current observations, there may be unknown bugs. So in order to avoid affecting the online, it is recommended to take it out separately

Check List

Tests

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

  • I checked and no code files have been changed.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

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[ti-chi-bot]

@ti-chi-bot: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
idc-jenkins-ci-tidb/unit-test	51d96a9	link	true	/test unit-test
idc-jenkins-ci-tidb/build	51d96a9	link	true	/test build
idc-jenkins-ci-tidb/check_dev_2	51d96a9	link	true	/test check-dev2
idc-jenkins-ci-tidb/mysql-test	51d96a9	link	true	/test mysql-test
idc-jenkins-ci-tidb/check_dev	51d96a9	link	true	/test check-dev

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