sync_diff_inspector: add sum aggregate

[Leavrth]

What problem does this PR solve?

Issue Number: ref #634

What is changed and how it works?

we can choose SUM as the aggregate operator instead of BIT_XOR.

Check List

Tests

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

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[3pointer]

rest LGTM

[lance6716]

rest lgtm

[ti-chi-bot]

@Leavrth: PR needs rebase.

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