There's a little buglet in #85387 (which was the PR that closed #84046), specifically, it doesn't account for the possibility that there's both a default/request **and** and a final pipeline, and that they can both touch the `@timestamp` field.

`IngestService#postIngest` was added in #85387, and it's intended that the logic there only runs **once**, after all the pipelines associated with the request have been executed. But as it's currently written, the logic actually runs after each individual pipeline runs.

The consequence of that is that if there's a default/request and a final pipeline in use for a document, and the final pipeline changes the timestamp field, the `rawTimestamp` recorded for the `IndexRequest` associated with the document will mistakenly use the value it sees after the default/request pipeline runs, and **not** the most correct one (from after when the final pipeline runs).

/cc @martijnvg 
server/src/main/java/org/elasticsearch/ingest/IngestDocument.java
|| value instanceof Integer
            || value instanceof Long
            || value instanceof Float
            || value instanceof Double
            || value instanceof Boolean
            || value instanceof ZonedDateTime) {
                return value;
            } else if (value instanceof Date date) {
                return date.clone();
            } else {
                throw new IllegalArgumentException("unexpected value type [" + value.getClass() + "]");
            }
    }
    public static Set<String> getAllFields(Map<String, Object> input) {
        return getAllFields(input, "");
    }
    @SuppressWarnings("unchecked")
    private static Set<String> getAllFields(Map<String, Object> input, String prefix) {
        Set<String> allFields = Sets.newHashSet();
        input.forEach((k, v) -> {
            allFields.add(prefix + k);
            if (v instanceof Map<?, ?> mapValue) {
                allFields.addAll(getAllFields((Map<String, Object>) mapValue, prefix + k + "."));
            }
        });
        return allFields;
    }
    /**
     * Executes the given pipeline with for this document unless the pipeline has already been executed
     * for this document.