Implement some "hint" banners in the admin panel

[msm-code]

Feature Category

• [ ] Correctness
• [x] User Interface / User Experience
• [ ] Performance
• [ ] Other (please explain)

Describe the problem

Sometimes it's not obvious that the system is in unhealthy state.

Describe the solution you'd like

We can detect some of these problems and show them in the /status endpoint. Ideas I have right now:

• Two agent groups have the same ursadb URL (probably a mistake/configuration error)
• There are too many datasets (especially many small datasets - compacting is needed)
• There are no connected agents (obviously a problem)

Describe alternatives you've considered