09461d03ea
* keep existing unified alert rules untouched
* move silences and other alertmanager files to the organization directory (only if it is a single organization deployment)
* assign the existing notification settings and routes to the first organization
* create default notification settings for each organization in the case of multi org deployment
(cherry picked from commit 5d0d7dcb3a)
Co-authored-by: Yuriy Tseretyan <yuriy.tseretyan@grafana.com>