chore: increase timeout on load tests (#419)

* chore: increase timeout on load tests

* increase vm timeout too

Author: tswast

.kokoro/load/common.cfg

@@ -8,3 +8,4 @@ action {
 }
 
 build_file: "python-bigquery-dataframes/.kokoro/build.sh"
+timeout_mins: 360

noxfile.py

@@ -290,6 +290,7 @@ def run_system(
     install_test_extra=True,
     print_duration=False,
     extra_pytest_options=(),
+    timeout_seconds=900,
 ):
     """Run the system test suite."""
     constraints_path = str(
@@ -311,7 +312,7 @@ def run_system(
         "--quiet",
         "-n=20",
         # Any individual test taking longer than 15 mins will be terminated.
-        "--timeout=900",
+        f"--timeout={timeout_seconds}",
         # Log 20 slowest tests
         "--durations=20",
         f"--junitxml={prefix_name}_{session.python}_sponge_log.xml",
@@ -395,6 +396,7 @@ def load(session: nox.sessions.Session):
         prefix_name="load",
         test_folder=os.path.join("tests", "system", "load"),
         print_duration=True,
+        timeout_seconds=60 * 60,
     )