docs: add a TROUBLESHOOTING.md file with tips for logging

TROUBLESHOOTING.md

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+# Troubleshooting steps
+
+## Enable logging of BQ Storage Read API session creation
+
+It can be helpful to get the BQ Storage Read API session to allow the BigQuery
+backend team to debug cases of API instability. The logs that share the session
+creation are in a module-specific logger. To enable the logs, refer to the
+following code sample:
+
+```python
+import logging
+import google.cloud.bigquery
+
+# Configure the basic logging to show DEBUG level messages
+log_formatter = logging.Formatter(
+    '%(asctime)s - %(levelname)s - %(message)s'
+)
+handler = logging.StreamHandler()
+handler.setFormatter(log_formatter)
+default_logger = logging.getLogger()
+default_logger.setLevel(logging.DEBUG)
+default_logger.addHandler(handler)
+to_dataframe_logger = logging.getLogger("google.cloud.bigquery._pandas_helpers")
+to_dataframe_logger.setLevel(logging.DEBUG)
+to_dataframe_logger.addHandler(handler)
+
+# Example code that touches the BQ Storage Read API.
+bqclient = google.cloud.bigquery.Client()
+results = bqclient.query_and_wait("SELECT * FROM `bigquery-public-data.usa_names.usa_1910_2013`")
+print(results.to_dataframe().head())
+```
+
+In particular, watch for the text "with BQ Storage API session" in the logs
+to get the streaming API session ID to share with your support person.