Improve search bar funcionality based on real life requirements

**Is your feature request related to a problem? Please describe.**
OWASP Nest search/filtering/ranking/sorting is crucial part of the functionality. Finally we're at the point where we understand how it should be implemented.

**Describe the solution you'd like**
We need to improve the search bar component tackling multiple problems:
- search request should go through the backend instead of direct algolia hits (more control, no unwanted interaction)
- in-house developed auto-suggestions (again, more control over the behavior, but requires also more work)
- text filtering for all entities (some work has been done [here](https://github.com/OWASP/Nest/pull/448))

This is combined into a single task to avoid merge conflicts and any misunderstandings leading to incompatibility and eventually more work.