### 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
if (supportsCopyTo()) {
            examples.add(
                new SyntheticSourceInvalidExample(
                    matchesPattern("field \\[field] of type \\[.+] doesn't support synthetic source because it declares copy_to"),
                    b -> {
                        syntheticSourceSupport(ignoreMalformed).example(5).mapping().accept(b);
                        b.field("copy_to", "bar");
                    }
                )
            );
        }
        for (SyntheticSourceInvalidExample example : examples) {
            Exception e = expectThrows(
                IllegalArgumentException.class,
                example.toString(),
                () -> createDocumentMapper(syntheticSourceMapping(b -> {
                    b.startObject("field");
                    example.mapping.accept(b);
                    b.endObject();
                }))
            );
            assertThat(e.getMessage(), example.error);
        }
    }
    @Override
    protected final <T> T compileScript(Script script, ScriptContext<T> context) {
        return ingestScriptSupport().compileScript(script, context);
    }
    protected abstract IngestScriptSupport ingestScriptSupport();
    protected abstract class IngestScriptSupport {