Move auth_type to top level per proto definition

- auth_type is field 5 at OssSqlDriverTelemetryLog level, not nested
- Remove driver_connection_params (not populated in Node.js driver)
- Export auth_type directly in sql_driver_log for connection events

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: samikshya-db

lib/telemetry/DatabricksTelemetryExporter.ts

@@ -52,7 +52,7 @@ interface DatabricksTelemetryLog {
         char_set_encoding?: string;
         process_name?: string;
       };
-      driver_connection_params?: any;
+      auth_type?: string;
       operation_latency_ms?: number;
       sql_operation?: {
         statement_type?: string;
@@ -301,10 +301,8 @@ export default class DatabricksTelemetryExporter {
       if (metric.latencyMs !== undefined) {
         log.entry.sql_driver_log.operation_latency_ms = metric.latencyMs;
       }
-      // Include driver connection params (auth type)
-      log.entry.sql_driver_log.driver_connection_params = {
-        auth_type: metric.driverConfig.authType,
-      };
+      // Include auth type at top level (proto field 5)
+      log.entry.sql_driver_log.auth_type = metric.driverConfig.authType;
     } else if (metric.metricType === 'statement') {
       log.entry.sql_driver_log.operation_latency_ms = metric.latencyMs;