[ML] Custom rules are not updated while the job is running

[valeriy42]

When we create a custom rule for an open anomaly detection job, e.g. using Kibana or the Anomaly Detection Job Update API, the rule is stored in the Java job configuration and passed to the native process, but the job configuration is not updated on the fly. This behavior can be reproduced in recent Elasticsearch versions, at least 8.13+.

The only workaround is to stop and restart the job.