Update templates for external monitoring

[mattkjames7]

Summary

This PR adds end-to-end remote observability support for both memgraph and memgraph-high-availability Helm charts by introducing:

• optional vmagentRemote support for Prometheus remote_write metrics export,
• optional vectorRemote sidecars for shipping Memgraph logs to Loki-compatible endpoints,
• chart value/template updates and README examples for configuring auth, labels, and namespaces.

It also improves HA behavior by adding safer cluster setup hook/retry handling and forcing mg-exporter rollout on relevant config changes.

Validation

• Adds a new CI workflow: .github/workflows/test-remote-monitoring.yaml
• Provisions a remote monitoring stack (scripts/remote-monitoring-stack.yaml)
• Verifies both metrics and logs ingestion with scripts/verify-remote-monitoring.sh for:
  • HA chart deployment
  • standalone chart deployment

Notes

• Includes minor formatting cleanup in charts/memgraph-lab/values.yaml.

[as51340]

Also, make sure to open a PR on docs for this 😄