PostgreSQL compatibility: `extract(milliseconds ...)` should preserve fractional milliseconds

Split out from #22247.

### Mismatch

`extract(milliseconds ...)` should preserve fractional milliseconds.

```sql
SELECT extract(milliseconds from timestamp '2020-01-01 00:00:12.345678');
```

PostgreSQL:

```text
12345.678
```

DataFusion:

```text
12345
```

### Expected behavior

For PostgreSQL-compatible SQL semantics, DataFusion should either match PostgreSQL's result or raise the same class of domain/semantic error.