build: add new task for integration tests of sync_diff_inspector

[joechenrh]

What problem does this PR solve?

Issue Number: ref #11672

What is changed and how it works?

Add new build task sync-diff-inspector-integration-test and change related task name to snake case.

Related CI change: PingCAP-QE/ci#3387

Check List

Tests

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

Questions

Will it cause performance regression or break compatibility?

Do you need to update user documentation, design documentation or monitoring documentation?

Release note

Please refer to [Release Notes Language Style Guide](https://pingcap.github.io/tidb-dev-guide/contribute-to-tidb/release-notes-style-guide.html) to write a quality release note.

If you don't think this PR needs a release note then fill it with `None`.

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[ti-chi-bot]

@joechenrh: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-verify	8ba8324	link	true	/test pull-verify

Full PR test history. Your PR dashboard.

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