### 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_
x-pack/plugin/mapper-aggregate-metric/src/test/java/org/elasticsearch/xpack/aggregatemetric/mapper/AggregateDoubleMetricFieldMapperTests.java
/**
     * Test setting an invalid value for the default_metric. An exception must be thrown
     */
    public void testInvalidDefaultMetric() {
        Exception e = expectThrows(
            MapperParsingException.class,
            () -> createDocumentMapper(
                fieldMapping(
                    b -> b.field("type", CONTENT_TYPE)
                        .field(METRICS_FIELD, new String[] { "value_count", "sum" })
                        .field(DEFAULT_METRIC, "invalid_metric")
                )
            )
        );
        assertThat(e.getMessage(), containsString("Metric [invalid_metric] is not supported."));
    }
    /**
     * Test setting a value for the default_metric that is not contained in the "metrics" field.
     * An exception must be thrown
     */
    public void testUndefinedDefaultMetric() {
        Exception e = expectThrows(
            MapperParsingException.class,
            () -> createDocumentMapper(
                fieldMapping(
                    b -> b.field("type", CONTENT_TYPE)
                        .field(METRICS_FIELD, new String[] { "value_count", "sum" })
                        .field(DEFAULT_METRIC, "min")
                )
            )