feat: integrate Grafana Alloy and Loki for metrics and logging

[Dyslex7c]

Changes

• Added scripts/monitoring/alloy-config.alloy- Grafana Alloy configuration that collects Nethermind container logs via the Docker socket and forwards them to Grafana Loki, and scrapes Nethermind Prometheus metrics (port 8008) and forwards them to Grafana remote write endpoint
• Updated sync-supported-chains.yml to start Grafana Alloy as a Docker sidecar after Sedge brings up the Nethermind node, and stop it gracefully before VM teardown to ensure buffered logs and metrics are flushed
• Labels aligned with central monitoring conventions (job, project, external_provider, Instance, Network, User) to ensure consistency with the Alloy integration in post-merge-smoke-tests

Types of changes

What types of changes does your code introduce?

• Bugfix (a non-breaking change that fixes an issue)
• New feature (a non-breaking change that adds functionality)
• Breaking change (a change that causes existing functionality not to work as expected)
• Optimization
• Refactoring
• Documentation update
• Build-related changes
• Other: Description

Testing

Requires testing

• Yes
• No

If yes, did you write tests?

• Yes
• No

Documentation

Requires documentation update

• Yes
• No

Requires explanation in Release Notes

• Yes
• No

Remarks

cc @cbermudez97 for review