Feat: make taskprocessing task types toggleable

[janepie]

• Resolves Toggle task types in admin settings assistant#157

Summary

Makes taskprocessing task types toggable in AI admin settings: disabled types will not be available and will not show up in e.g. the assistant.
Task types are enabled by default. The values are stored in a new appconfig db record.

Before:

After:

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 feat: describe task type disabling documentation#12424
• Backports requested where applicable (ex: critical bugfixes) not applicable

[marcelklehr]

Yay 🎉 Congrats on your first server PR :)

[janepie]

@AndyScherzinger can you force merge? I am pretty sure the Cypress runner failing is not my fault as it's failing for all PRs right now 😅

[welcome]

Thanks for your first pull request and welcome to the community! Feel free to keep them coming! If you are looking for issues to tackle then have a look at this selection: https://github.com/nextcloud/server/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22

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