feat: Add funding_fee to backtest results

closes #11699

tests/optimize/test_backtesting.py

@@ -828,6 +828,7 @@ def test_backtest_one(default_conf, mocker, testdatadir) -> None:
                     },
                 ],
             ],
+            "funding_fees": [0.0, 0.0],
         }
     )
     pd.testing.assert_frame_equal(results, expected)

tests/optimize/test_backtesting_adjust_position.py

@@ -80,6 +80,7 @@ def test_backtest_position_adjustment(default_conf, fee, mocker, testdatadir) ->
             "is_short": [False, False],
             "open_timestamp": [1517251200000, 1517283000000],
             "close_timestamp": [1517263200000, 1517285400000],
+            "funding_fees": [0.0, 0.0],
         }
     )
     results_no = results.drop(columns=["orders"])