[FEATURE] Offer external storage location for ISM history logs

[spapadop]

Is your feature request related to a problem?
The ISM history logs are usually small enough. Luckily, there are already some settings available to change the rollover time and generally control these indices, as explained here.

In any case, these indices can take up space and number of shards (by default up to 60).
Especially for small test clusters, this can be more than half of the total shards.

What solution would you like?
Just like security audit logs, offer the possibility of storing the ISM history logs externally, to a different OpenSearch cluster or a webhook.

What alternatives have you considered?
There are no real alternatives to the above.

Do you have any additional context?
Many clusters are actually offered as a service to customers, so centralising the system logs somewhere outside that cluster, offloading any system activity from it, makes sense.