Avoid reloading Botkube when notification preferences change via remote config

[pkosiec]

Overview

Currently, we restart Botkube for edit sourcebindings, enable/disable actions, but we don't for the enable/disable notifications command in the ConfigMap-based config. But, in order to achieve the same for remote configuration, we would need to change internal logic so that we:

• update notifications for a given channel (this needs a single state with all notifier references)
• get the diff and extract the channel which changed notifications
• send message to a given channel (channel-based routing map is needed + this needs a rework for the notifier executor)
  • updating notifications should happen after ConfigMap update, not before
  • same for remote config reloader

Reason

Improve UX

See also

Remote config reloader PR: #1006