Improve calculation method of project.pipelineAnalytics.timeSeries to attribute duration to each aggregation slot

The first version of the project.pipelineAnalytics.timeSeries implementation attributes the entirety of a pipeline duration to the day where the pipeline started, because that was the simplest approach and allowed us to unblock the frontend. This issue follows up to improve the calculation method to attribute the duration of the pipeline over the time series according to the exact duration that happened on a particular aggregation (day or hour).

As an example, let's say we are looking at a time window going from Jan 1st to Jan 7th UTC, and a single pipeline started on noon Jan 2nd with a duration of 3 days. With the existing calculation method, the time series would show a duration of 3 days on Jan 2nd. With this issue, we want the time series to show Jan 2nd -> 12 hours, Jan 3rd -> 24 hours, Jan 4th -> 24 hours, Jan 5th -> 12 hours.

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