BotKube controller refactor

[PrasadG193]

Is your feature request related to a problem? Please describe.
Refactor BotKube controller code to make it HA compatible. As of now, running BotKube in multiple replicas initiate multiple instances of controller i.e watchers and notifiers.

[mszostok]

We changed the Botkube architecture, now we have the plugin system. However, to make this solution HA, we would require to run plugins outside the Botkube core pod. For now, we don't require such setup, but it will be possible if needed.