[WIP] Add task processing streaming support

[julien-nc]

Summary

This is related with #60167 and nextcloud/integration_openai#366

This adds support for intermediate (streamed) results of task processing tasks.

• Add a new interface for task processing providers: ISynchronousProgressiveProvider. This new interface includes an additional callback passed as a param to the provider's process method: reportOutput that can be used to set intermediate results.
• Add an endpoint for exApps to set intermediate results (without setting the task status to FINISHED)
• Adjust the manager to correctly use ISynchronousProgressiveProvider providers

TODO

• Decide if it's fine to NOT update the task in DB if notify_push is available

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)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI