## Is your feature request related to a problem?

Currently the funnel time to convert query (added in #4947) only allows measuring time it took to a specific step from the one immediately preceding it. However it'd be useful to also bin by the _total_ time to convert – how long it took to complete the funnel (reach the last step) from entering it (reaching the first step).

## Describe the solution you'd like

Right now `ClickhouseFunnelTimeToConvert` uses only `Filter.funnel_to_step`. It should also be able to work with `Filter.funnel_from_step`. If `funnel_from_step` is `0` and `funnel_to_step` is `len(steps)-1`, that'd be the total time to convert.

#### *Thank you* for your feature request – we love each and every one!

ee/clickhouse/queries/funnels/test/test_funnel_time_to_convert.py
"interval": "day",
                "date_from": "2021-06-07 00:00:00",
                "date_to": "2021-06-13 23:59:59",
                "funnel_to_step": 1,
                "funnel_window_days": 7,
                "bin_count": 7,
                "events": [
                    {"id": "step one", "order": 0},
                    {"id": "step two", "order": 1},
                    {"id": "step three", "order": 2},
                ],
            }
        )
        funnel_trends = ClickhouseFunnelTimeToConvert(filter, self.team, ClickhouseFunnel)
        results = funnel_trends.run()
        
        self.assertEqual(
            results,
            [
                (2220.0, 2),  
                (13732.0, 0),  
                (25244.0, 0),  
                (36756.0, 0),
                (48268.0, 0),
                (59780.0, 0),
                (71292.0, 1),  
                (82804.0, 0),
            ],
        )
    def test_basic_unordered(self):