Add CI Workflow to Validate Tutorials for Backward Compatibility and Online

**Is your feature request related to a problem? Please describe.**
Yes. Tutorials and example scripts (e.g., `milvus_example.py`) can silently break when there are updates to online stores or deprecated dependencies. There's no CI to validate these examples after such changes, which leads to user complaints about broken tutorials — especially after major updates to the development of specific online stores.

**Describe the solution you'd like**
Add a GitHub Actions CI workflow that automatically:
- Runs all tutorials and example scripts under `examples/online_store/**`.
- Validates compatibility whenever core components (like online stores) are modified.
- Surfaces issues when changes break tutorials, ensuring everything stays in sync.

This would catch regressions early and align examples with development changes.

**Describe alternatives you've considered**
- Manual testing of tutorials before releases (not scalable).
- Relying on user reports or contributors to notice breakages (reactive, not ideal).