Get rid of old errata implementation

As a consequence of several errata updates in our codebase, mostly https://github.com/AlmaLinux/albs-web-server/pull/718 and https://github.com/AlmaLinux/albs-web-server/pull/998, we keep code from the old errata data model and workflow, and we need to get rid of it.

I'm leaving some references to this ticket around web server code, but scope and specific actions are yet to be described.

Also, here's a list of things that we can remove from the current implementation:
- [ ] Get rid of `reboot_suggested` as looks like it's not used anymore
- [ ] [Stop mapping errata packages upon build done](https://github.com/AlmaLinux/build-system/issues/402)