Optimizer casts decimals to different values on different platforms

[andygrove]

Describe the bug

See ignored test in #3790

To Reproduce

    /// This query produces different plans depending on operating system
    /// Linux:   Decimal128(Some(7000000000000000195487369212723200),38,33)
    /// Windows: Decimal128(Some(6999999999999999042565864605876224),38,33)
    #[tokio::test]
    #[ignore]
    async fn q17_expected_plan() -> Result<()> {
        expected_plan(17).await
    }
```

**Expected behavior**
Is this expected?

**Additional context**
None