### Elasticsearch Version

main

### Installed Plugins

_No response_

### Java Version

_bundled_

### OS Version

all

### Problem Description

When you configure an `aggregate_metric_double` with `ignore_malformed: true` and send a malformed value we create an `_ignored` field with three values, `field.value_count`, `field.min`, and `field.max`. This is the only top "composite" field that creates `_ignored` values for its children. Things like shape only create `field` in `_ignored`. Is there a good reason for `aggregate_metric_double` to be different?

### Steps to Reproduce

see above

### Logs (if relevant)

_No response_
test/framework/src/main/java/org/elasticsearch/index/mapper/MapperTestCase.java
+ mapper.name()
            + "] was ["
            + mapper.typeName()
            + "].";
    }
    public record SyntheticSourceExample(
        CheckedConsumer<XContentBuilder, IOException> inputValue,
        CheckedConsumer<XContentBuilder, IOException> result,
        CheckedConsumer<XContentBuilder, IOException> mapping
    ) {
        public SyntheticSourceExample(Object inputValue, Object result, CheckedConsumer<XContentBuilder, IOException> mapping) {
            this(b -> b.value(inputValue), b -> b.value(result), mapping);
        }
        private void buildInput(XContentBuilder b) throws IOException {
            b.field("field");
            inputValue.accept(b);
        }
        private String expected() throws IOException {
            XContentBuilder b = JsonXContent.contentBuilder().startObject().field("field");
            result.accept(b);
            return Strings.toString(b.endObject());
        }
    }
    public record SyntheticSourceInvalidExample(Matcher<String> error, CheckedConsumer<XContentBuilder, IOException> mapping) {}
    public interface SyntheticSourceSupport {
        /**
         * Examples that should work when source is generated from doc values.
         */
        SyntheticSourceExample example(int maxValues) throws IOException;
        /**