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