Integrated Alerting: Additional context to alerts to better convey issue detected

User Impact:
User receives alert notification without any details e.g about environment, service, node, template, threshold.
Steps to reproduce:

• Create some alert rules e.g. Node high CPU load

• Emulate some alerts for several nodes

• Add notification channel, e.g. slack

• Check notification received about alerts

Actual result:
The list of alerts contains several items for different nodes.
Notification about alert doesn't contain any details from labels in the Alerts list
The notification is sent only once for all alerts in the list.

Expected result:
Users can receive notifications about every item in the Alerts list.
The notification contains details from Alerts labels (node-name, service-name etc.)