Move non time critical background tasks to maintenance window

[PVince81]

With nextcloud/server#30945 it will be possible to move background jobs to times where the server is less busy. We have some tasks that currently run at a fixed interval, where it might make sense to move them for the chance of yielding better performance.

• lib/BackgroundJob/ETLJob.php - unchanged
• lib/BackgroundJob/TrainJobIpV4.php
• lib/BackgroundJob/TrainJobIpV6.php

For each TimedJob, add the TIME_INSENSITIVE flag, when:

• if can be run once a day only
• and if it causes a high load

[PVince81]

seems the training is happening every 24 hours, so it would likely make sense to move those to the maintenance window @ChristophWurst ?

[PVince81]

PR here: #619

ETL only runs every 6 hours so not sure, I didn't cover it. let's leave it unchanged then