[Test] Clean up benchmarks python scripts. (#33919)

Cleans up unnecessary imports. Adds file name when dumping contents to
log. Makes `prometheus.py` executable.

tools/run_tests/performance/bq_upload_result.py

@@ -15,8 +15,6 @@
 
 # Uploads performance benchmark result file to bigquery.
 
-from __future__ import print_function
-
 import argparse
 import calendar
 import json

tools/run_tests/performance/patch_scenario_results_schema.py

@@ -15,15 +15,10 @@
 
 # Use to patch schema of existing scenario results tables (after adding fields).
 
-from __future__ import print_function
-
 import argparse
-import calendar
 import json
 import os
 import sys
-import time
-import uuid
 
 gcp_utils_dir = os.path.abspath(
     os.path.join(os.path.dirname(__file__), "../../gcp/utils")

tools/run_tests/performance/prometheus.py

@@ -1,5 +1,4 @@
 #!/usr/bin/env python3
-
 # Copyright 2022 The gRPC Authors
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
@@ -320,7 +319,11 @@ def main() -> None:
     )
     processed_data["testDurationSeconds"] = float(end_time) - float(start_time)
 
-    logging.debug(json.dumps(processed_data, sort_keys=True, indent=4))
+    logging.debug(
+        "%s: %s",
+        args.export_file_name,
+        json.dumps(processed_data, sort_keys=True, indent=4),
+    )
 
     with open(args.export_file_name, "w", encoding="utf8") as export_file:
         json.dump(processed_data, export_file, sort_keys=True, indent=4)