### 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
public Expression field() {
        return field;
    }
    public Expression decimals() {
        return decimals;
    }
    @Override
    public DataType dataType() {
        return field.dataType();
    }
    @Override
    public ScriptTemplate asScript() {
        throw new UnsupportedOperationException("functions do not support scripting");
    }
    @Override
    public ExpressionEvaluator.Factory toEvaluator(Function<Expression, ExpressionEvaluator.Factory> toEvaluator) {
        DataType fieldType = dataType();
        if (fieldType == DataTypes.DOUBLE) {
            return toEvaluator(toEvaluator, RoundDoubleNoDecimalsEvaluator::new, RoundDoubleEvaluator::new);
        }
        if (fieldType == DataTypes.INTEGER) {
            return toEvaluator(toEvaluator, identity(), RoundIntEvaluator::new);
        }
        if (fieldType == DataTypes.LONG) {
            return toEvaluator(toEvaluator, identity(), RoundLongEvaluator::new);
        }
        if (fieldType == DataTypes.UNSIGNED_LONG) {
            return toEvaluator(toEvaluator, identity(), RoundUnsignedLongEvaluator::new);
        }
        throw EsqlIllegalArgumentException.illegalDataType(fieldType);