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
throw new IllegalArgumentException(result.errorMessage);
            }
        }
        return cast(path, context, clazz);
    }
    /**
     * Returns the value contained in the document with the provided templated path
     * @param pathTemplate The path within the document in dot-notation
     * @param clazz The expected class fo the field value
     * @return the value for the provided path if existing, null otherwise
     * @throws IllegalArgumentException if the pathTemplate is null, empty, invalid, if the field doesn't exist,
     * or if the field that is found at the provided path is not of the expected type.
     */
    public <T> T getFieldValue(TemplateScript.Factory pathTemplate, Class<T> clazz) {
        return getFieldValue(renderTemplate(pathTemplate), clazz);
    }
    /**
     * Returns the value contained in the document for the provided path as a byte array.
     * If the path value is a string, a base64 decode operation will happen.
     * If the path value is a byte array, it is just returned
     * @param path The path within the document in dot-notation
     * @return the byte array for the provided path if existing
     * @throws IllegalArgumentException if the path is null, empty, invalid, if the field doesn't exist
     * or if the field that is found at the provided path is not of the expected type.
     */
    public byte[] getFieldValueAsBytes(String path) {
        return getFieldValueAsBytes(path, false);
    }
    /**
     * Returns the value contained in the document for the provided path as a byte array.