[helm] Extend Lint Checks to Include All Examples for Full Validation

[pkoutsovasilis]

The current helm lint check in our CI pipeline is insufficient. While helm template may pass, helm lint can still fail due to additional validation that helm template does not perform. We should extend the Helm lint checks to validate all the examples in the Helm chart to ensure consistency and prevent errors during deployment.

Example https://github.com/helm/helm/issues/7756#issuecomment-617889123

• Steps to Reproduce:
  1. Run helm template ./deploy/helm/elastic-agent -f ./deploy/helm/elastic-agent/examples/kubernetes-default/agent-kubernetes-values.yaml and observe that it passes.
  2. Run helm lint ./deploy/helm/elastic-agent -f ./deploy/helm/elastic-agent/examples/kubernetes-default/agent-kubernetes-values.yaml on the same chart and notice that it fails, demonstrating inconsistencies.

[elasticmachine]

Pinging @elastic/elastic-agent-control-plane (Team:Elastic-Agent-Control-Plane)