Alerting: UI to addres notification resources by UID

During migration to the new K8s-style APIs, we made a decision to use LIST endpoint with a filter by resource title to get the specification for the edit page. This approach has a problem - some reverse proxies do not correctly handle `/` and `\` in URLs which causes problems with accessing a resource via UI. To solve this problem UI needs to migrate to GET endpoints that refer to resources by `metadata.name`. To fully close the cycle we need to update provisioning export APIs to support reference by that name.