### Elasticsearch Version

8.11.0

### Installed Plugins

_No response_

### Java Version

_bundled_

### OS Version

MacOS

### Problem Description

The following ESQL statement reports and unhandled error:

```
from index | eval round([1.2])
```

Returns the rror:
```
class_cast_exception - class java.util.ImmutableCollections$ListN cannot be cast to class java.lang.Number (java.util.ImmutableCollections$ListN and java.lang.Number are in module java.base of loader 'bootstrap')
```

### Steps to Reproduce

See above

### Logs (if relevant)

_No response_
x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/scalar/math/Round.java
}
    private static <T, U> BiFunction<T, U, T> identity() {
        return (t, u) -> t;
    }
    private ExpressionEvaluator.Factory toEvaluator(
        Function<Expression, ExpressionEvaluator.Factory> toEvaluator,
        BiFunction<ExpressionEvaluator, DriverContext, ExpressionEvaluator> noDecimals,
        TriFunction<ExpressionEvaluator, ExpressionEvaluator, DriverContext, ExpressionEvaluator> withDecimals
    ) {
        var fieldEvaluator = toEvaluator.apply(field());
        if (decimals == null) {
            return dvrCtx -> noDecimals.apply(fieldEvaluator.get(dvrCtx), dvrCtx);
        }
        var decimalsEvaluator = Cast.cast(decimals().dataType(), DataTypes.LONG, toEvaluator.apply(decimals()));
        return dvrCtx -> withDecimals.apply(fieldEvaluator.get(dvrCtx), decimalsEvaluator.get(dvrCtx), dvrCtx);
    }
    @Override
    public int hashCode() {
        return Objects.hash(field, decimals);
    }
    @Override
    public boolean equals(Object obj) {
        if (obj == null || obj.getClass() != getClass()) {
            return false;
        }
        Round other = (Round) obj;
        return Objects.equals(other.field, field) && Objects.equals(other.decimals, decimals);
    }
}