Enhance helm tests for Monitoring - verify Istio Dashboards

Enhance Helm tests for monitoring to verify istio dashboards are present

A/C:

• add Istio Dashboard verification to current tests
  • Istio Control Plane
  • Istio Mesh
  • Istio Performance
  • Istio Service
  • Istio Wasm Extension Dashboard
  • Istio Workload

Added 1/13/22:

• Test that the charts within each dashboard are populated with data