chore(csharp/test/Drivers/Databricks): Add IsCITesting in DatabricksTestConfiguration (#3153)

## Motivation 

There are some E2E test in Databricks driver tests (
e.g.`StatusPollerKeepsQueryAlive` in `StatementTest`) should be skipped
for various reasons, we can include property `IsCITesting` in
`DatabricksTestConfiguration` to indicates if the current test
environment is run in the CI.

### Changes
- Added `IsCITesting` in `DatabricksTestConfiguration` with default
value `false`

Author: jackyhu-db

csharp/test/Drivers/Databricks/E2E/DatabricksTestConfiguration.cs

@@ -45,5 +45,8 @@ public class DatabricksTestConfiguration : SparkTestConfiguration
 
         [JsonPropertyName("traceStateEnabled"), JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingDefault)]
         public string TraceStateEnabled { get; set; } = string.Empty;
+
+        [JsonPropertyName("isCITesting"), JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingDefault)]
+        public bool IsCITesting { get; set; } = false;
     }
 }