make docstring test work in all environments (#896)

# Pull Request

## Title

Make inline unit tests that display Pandas DataFrame work in all
environments, regardless of terminal width.

---

## Description

Inline tests in docstrings sometimes fail if the terminal width does not
match the expected one and the pandas DataFrame got displayed
differently.

- **Issue link**: Closes #895 

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## Type of Change

- 🛠️ Bug fix
- 📝 Documentation update
- 🧪 Tests

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## Testing

Unit tests should pass now

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conftest.py

@@ -52,6 +52,12 @@ def pytest_configure(config: pytest.Config) -> None:
         except ImportError:
             pass
 
+    # Set pandas display options to make inline tests stable.
+    import pandas  # pylint: disable=import-outside-toplevel
+
+    pandas.options.display.width = 120
+    pandas.options.display.max_columns = 10
+
     # Create a temporary directory for sharing files between master and worker nodes.
     if is_master(config):
         # Add it to the config so that it can passed to the worker nodes.

mlos_bench/mlos_bench/storage/__init__.py

@@ -143,11 +143,12 @@
 >>> # Retrieve the results of all Trials in the Experiment as a DataFrame.
 >>> experiment_data.results_df.columns.tolist()
 ['trial_id', 'ts_start', 'ts_end', 'tunable_config_id', 'tunable_config_trial_group_id', 'status', 'config.param1', 'result.objective_metric']
->>> experiment_data.results_df.drop(columns=["ts_start"])
-   trial_id  ... result.objective_metric
-0         1  ...                      42
-<BLANKLINE>
-[1 rows x 7 columns]
+>>> # Drop the timestamp columns to make it a repeatable test.
+>>> experiment_data.results_df.drop(columns=["ts_start", "ts_end"])
+   trial_id  tunable_config_id  tunable_config_trial_group_id     status  config.param1  result.objective_metric
+0         1                  1                              1  SUCCEEDED             50                       42
+
+[1 rows x 6 columns]
 
 See Also
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