Improve snapshot generation

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**Is your feature request related to a problem? Please describe.**

For chapters get new items method returns entities filtered by `is_active` status. However, it's not enough as sometimes repositories can still be empty.

**Describe the solution you'd like**

The snapshot processing job needs to utilize `active_chapters` manager instead of using custom filter.
The same approach has to be applied for all kind of entities (projects, releases, etc)

**Are you going to work on implementing this?**

- [ ] Yes
- [x] No

**Additional context**