Avoid Java Temp Files in task creation

[fm3]

• During task creation, we no longer use java’s own temporary file code (see reasons in linked issue below), but instead use a custom temporary file service.
• The initial data requests are no longer sent in parallel to the tracingstore but instead sequentially, to avoid overloading the tracingstore (new function Fox.serialSequenceBox)

URL of deployed dev instance (used for testing):

• https://taskcreationnotempfiles.webknossos.xyz

Steps to test:

• Create volume or hybrid task type
• try to create (hundreds of) tasks with initial volume data
• should not fail

Issues:

• fixes Server Errors when sending temporary files (JDK regression?) #6173

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• Updated (unreleased) changelog
• Needs tracingstore update after deployment
• Ready for review

[jstriebel]

Props for digging into this, I think the solution is good. Maybe we should also add a comment about the bug in the code (e.g. in TempFileService)? See my two comments below, besides this LGTM 👍

[fm3]

Thanks for your feedback! I implemented the suggestions and also noticed another bug, where slashes in the prefix would lead to wrong file paths (so I am removing those now). Could you have another look?

[jstriebel]