Fix soud intervals

[jredrejo]

Summary

1. Ensure SOUD sync happens at regular intervals
2. Ensure sync is not scheduled by zeroconf is a sync has been previously scheduled
3. Clean failed syncinc tasks and updates UserSyncStatus to avoid staled states
4. Whenever the server accepts a sync, it will send the syncing interval so the client will use it to schedule the new syncing.

References

Closes: #8236
Fixes "Possible that sync jobs can get duplicated for the same server when the server is restarted" from https://www.notion.so/learningequality/Single-User-Syncing-Hack-Session-60-mins-bfb609b7d7de47b1af1e73b6446e3cbd

Reviewer guidance

Restart several times the server or the synced server and check everything is working fine

Testing checklist

• Contributor has fully tested the PR manually
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Reviewer checklist

• Automated test coverage is satisfactory
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• PR has been tested for accessibility regressions
• External dependency files were updated if necessary (yarn and pip)
• Documentation is updated
• Contributor is in AUTHORS.md

[rtibbles]

I think adding a sync_interval argument to the sync command to both flag that we need to schedule a new sync and also how long we should wait.