Task Data Background Refetching

[jjoderis]

Summary

Instead of fetching the available tasks from all available engines for every user on a small timeout the task data is now served from the database. To ensure that the user has access to up to date information, this PR extends the deployment refetch loop to also refetch the task data from the available engines and update the database if necessary.
The loop runs once for all users as long as at least a single user is connected to the MS. See #747

Details

• adjusted the database schema to create a one-to-many relation between user tasks and instances
• adjusted the database schema for user tasks to reflect that the entries are now initialized with all relevant data instead of postponing setting these values to the first time they are requested by a user (before the html was written to the database when the first user tried to open the user task in the tasklist)
• added a new step to the deployment refetching loop that fetches the newest data for user tasks on available engines and writes updated values to the database
• changed all components that got their task data from the engines to fetch it from the database instead now

[github-actions]

✅ Successfully created Preview Deployment.

https://pr-751---ms-server-staging-c4f6qdpj7q-ew.a.run.app