Add lido-exporter alert rules and alertmanager for monitoring stack

[khalifaa55]

Changes:

• Include lido-exporter alerts for penalties and exit requests metrics.
• Include Prometheus alertmanager to Prometheus and Grafana
• Add Grafana OnCall plugin to Grafana

Types of changes

What types of changes does your code introduce?
Put an x in the boxes that apply

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Other (please describe):

Testing

Requires testing

• Yes
• No

In case you checked yes, did you write tests?

• Yes
• No

[AntiD2ta]

Suggested change

	annotations:
	summary: "Exit request detected"
	description: "An exit request has been detected for node operator {{ $labels.node_operator_id }}. Prompt action is required to exit the requested validators."
	annotations:
	summary: "Exit requests detected"
	description: "One or more exit requests have been detected for node operator {{ $labels.node_operator_id }}. Prompt action is required to exit the requested validators."