[BUG] timestampdiff return wrong schema in V2

[xinyual]

What is the bug?
The wrong schema we use for function timestampdiff.

How can one reproduce the bug?
Create any index. Then run ppl: source=demo | eval f = timestampdiff(YEAR, '1997-01-01 00:00:00', '2001-03-06 00:00:00') | fields f
Then it returns

{
    "schema": [
        {
            "name": "f",
            "type": "timestamp"
        }
    ],
    "datarows": [
        [
            4
        ]
    ],
    "total": 1,
    "size": 1
}

What is the expected behavior?
The schema should not be timestamp. Int or long could be better.

What is your host/environment?

• OS: [e.g. iOS]
• Version [e.g. 22]
• Plugins

Do you have any screenshots?
If applicable, add screenshots to help explain your problem.

Do you have any additional context?
Add any other context about the problem.

[LantaoJin]

With Calcite, the schema of timestampdiff will return integer. Mark it as a breaking change.

[LantaoJin]

Resolved by #3473

[qianheng-aws]

CalciteDateTimeFunctionIT::testTimestampDiff still failed caused by wrong schema