feat(TaskProcessing): Add more task types

[marcelklehr]

Summary

This creates three new task types. One is a chat task type that will make it easier to apply prompt templates for Assistant's LLM Chat interface. The other two are implemented already in llm2 (and also in integration_openai i think), so adding them here, allows to have a canonical definition.

Todo

• Discuss whether the I/O params are well chosen

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)

[julien-nc]

If you feel like adding it, we could use a "reformulate" task type as well.