Document Observability aspect of the solution

[devlace]

DoD:

• The following is documented:
  • What Telemetry is recorded and how it is recorded
  • Synapse pipeline run metrics (both from within Synapse workspace and from Log Analytics)
  • Custom metrics of the pipeline run sent to AppInsights via OpenCensus library
  • Where to look at them
  • Screenshots of the telemetry from Log Analytics, Synapse workspace, AppInsights
  • Example of an insight that can be viewed
• These are documented here in this section of the main README: https://github.com/Azure-Samples/modern-data-warehouse-dataops/blob/e2e/parking-sensors-synapse/e2e_samples/parking_sensors_synapse/README.md#observability--monitoring