feat(taskprocessing): add cleanup flag to tasks

[julien-nc]

Summary

This is useful for the assistant audio chat for example. We don't cleanup the chat message history so we need to prevent cleaning up the AudioChat tasks. Those tasks are deleted when the chat history is deleted.

Changes proposed in this PR:

• Move TaskProcessingApiController::extractFileIdsFromTask to OCP\TaskProcessing\IManager to be able to use it elsewhere
• Add the cleanup column to oc_taskprocessing_tasks
• Adjust the OC\TaskProcessing\Db\Task entity class
• Change the cleanup logic: It used to delete the old tasks and then the old files (based on their MTime) in appData/TaskProcessing. It now gets the list of old tasks to cleanup, gets the list of output files for those tasks and delete them. It then deletes the old tasks.
• Bump NC version number
• Generate autoload files
• Implement a taskprocessing:task:cleanup occ command
• Move the cleanup methods from the bg job class to the manager so they can be used by the command and the bg job

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[oleksandr-nc]

lgtm

[oleksandr-nc]

documentation update: nextcloud/documentation#13500

[DaphneMuller]

Feedback from @ChristophWurst : Server template was not followed and documentation requirements are lacking