[Maintenance]: Automate changelog and versioning

[Mark90]

The orchestrator-ui-library uses https://github.com/changesets/changesets to make maintaining the changelog + keeping track of patch/minor/major changes, an integral part of the development process. I think it'd be nice if we start using that (or something better suited for Python) for the orchestrator-core as well.

For reference:

• The orchestrator-ui-library's changelog document https://github.com/workfloworchestrator/orchestrator-ui-library/blob/main/packages/orchestrator-ui-components/CHANGELOG.md
• Individual releases are also maintained https://github.com/workfloworchestrator/orchestrator-ui-library/releases