Implement driver.Pinger interface for druid_api_sql_driver

[k-anshul]

The druid SQL driver(runtime/drivers/druid/druidsqldriver/druid_api_sql_driver.go) does not implement driver.Pinger interface.
This means the conn.Ping method does not make any API calls.
We use Ping method in our runtime health_checks. Without properly implemented Ping methods these checks can miss issues with OLAP connectivity.

• Implement Ping method. My impression is that we can use GET /status/health(https://druid.apache.org/docs/26.0.0/operations/api-reference/#process-information) endpoint for the same but confirm the same with @pjain1

[pjain1]

what about metrics view check here. They should run irrespective of Ping and return health check error?

[k-anshul]

The metrics_view check only report the number of metrics_view in error state and adds a separate log explaining the full error.
We can't fail health checks if metrics view are in error state since there can be multiple reasons for metrics view to be in error state and not just OLAP connectivity error.
To explicitly rely on OLAP connectivities we have explicit Pings.