SILKIT-1525: Use bulk-update endpoint of dashboard backend service

[VDanielEdwards]

Subject

These changes allow the dashboard client in SIL Kit to use the bulk-update endpoint (currently only available in a feature branch of the dashboard that is not publically available).

It allows for much larger simulations, as multiple changes can be combined into a single HTTP request.

Instructions for review / testing

Developer checklist (address before review)

• [x] Changelog.md updated
• [ ] Prepared update for depending repositories
• [x] Documentation updated (public API changes only)
• [ ] API docstrings updated (public API changes only)
• [x] Squash and merge → proper PR title

[VDanielEdwards]

NOTE: The branch was rebased onto the (soon-to-be-merged) branch dev_disable_broken_ubuntu1804_uploads from PR-73. Therefore, there will be a final rebase onto main after that one was merged.

[VDanielEdwards]

Hab ich richtig gesehen, dass die Optimierung nur über ExperimentalEnableDashboardBulkUpdates in der Konfigdatei aktivierbar ist und über CLI immer aus ist? Dann dokumentiere ich es so im Dashboard README. :)

I'm likely going to get some feedback from stakeholders today, so it's probably best if you wait until afternoon 👍 @NadegeNag

[VDanielEdwards]

@VDanielEdwards Note-to-Self: Check where the registry configuration schema is located and maintained (it is available in the schema store, but not in the sil-kit repository ?).

[VDanielEdwards]

@KonradBkd we replaced the flag with auto-detection of the bulk-update availability. The code has been streamlined slightly.

[VDanielEdwards]

LGTM (except the obsolete comment)

Also removed the obsolete documentation changes, and reworded the changelog entry.