Remove ursadb module from this project

[msm-code]

Feature Category

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

Describe the problem

There is no reason to keep ursadb as a submodule here. We're forcing end-users (and github CI) to compile it from source every time, and that takes a quite long time.

Describe the solution you'd like

We should just host ready build images and binaries, use them in dockerfiles and recommend to users.

Describe alternatives you've considered

No alternatives - but this is not a critical issue.