Address PR #321 review comments: Fix ExecContext telemetry timing and CloseOperation error tracking

This commit addresses two key review comments from @vikrantpuppala on PR #321:

1. **ExecContext timing fix**: Capture execution start time BEFORE running query
   - Now captures `executeStart := time.Now()` before `runQuery()` call
   - Uses `BeforeExecuteWithTime()` with pre-captured timestamp
   - Matches the pattern already implemented in QueryContext
   - Ensures telemetry accurately measures actual query execution time

2. **CloseOperation error tracking**: Capture cleanup errors in telemetry
   - Added `closeOpErr` variable to track CloseOperation failures
   - Includes CloseOperation errors in telemetry's deferred function
   - Provides observability for resource cleanup issues
   - Operation still returns success to caller (cleanup is best-effort)

These changes ensure telemetry captures the complete statement lifecycle,
including both execution timing and cleanup operations, without impacting
the caller's error handling semantics.

Co-authored-by: Isaac

Author: samikshya-db

connection.go

@@ -125,25 +125,34 @@ func (c *conn) ExecContext(ctx context.Context, query string, args []driver.Name
 
 	corrId := driverctx.CorrelationIdFromContext(ctx)
 
+	// Capture execution start time for telemetry before running the query
+	executeStart := time.Now()
 	var pollCount int
 	exStmtResp, opStatusResp, err := c.runQuery(ctx, query, args, &pollCount)
 	log, ctx = client.LoggerAndContext(ctx, exStmtResp)
 	stagingErr := c.execStagingOperation(exStmtResp, ctx)
 
 	// Telemetry: track statement execution
 	var statementID string
+	var closeOpErr error // Track CloseOperation errors for telemetry
 	if c.telemetry != nil && exStmtResp != nil && exStmtResp.OperationHandle != nil && exStmtResp.OperationHandle.OperationId != nil {
 		statementID = client.SprintGuid(exStmtResp.OperationHandle.OperationId.GUID)
-		ctx = c.telemetry.BeforeExecute(ctx, c.id, statementID)
+		// Use BeforeExecuteWithTime to set the correct start time (before execution)
+		ctx = c.telemetry.BeforeExecuteWithTime(ctx, c.id, statementID, executeStart)
 		defer func() {
 			finalErr := err
 			if stagingErr != nil {
 				finalErr = stagingErr
 			}
+			// Include CloseOperation error in telemetry if it occurred
+			if closeOpErr != nil && finalErr == nil {
+				finalErr = closeOpErr
+			}
 			c.telemetry.AfterExecute(ctx, finalErr)
 			c.telemetry.CompleteStatement(ctx, statementID, finalErr != nil)
 		}()
 		c.telemetry.AddTag(ctx, "poll_count", pollCount)
+		c.telemetry.AddTag(ctx, "operation_type", telemetry.OperationTypeExecuteStatement)
 	}
 
 	if exStmtResp != nil && exStmtResp.OperationHandle != nil {
@@ -156,6 +165,7 @@ func (c *conn) ExecContext(ctx context.Context, query string, args []driver.Name
 			})
 			if err1 != nil {
 				log.Err(err1).Msg("databricks: failed to close operation after executing statement")
+				closeOpErr = err1 // Capture for telemetry
 			}
 		}
 	}