Gets a double number of man-days that represents
duration. The number of man-days is computed from the project
NDepend.TechnicalDebt.DebtSettings.
NDepend.TechnicalDebt.DebtSettings.NumberOfWorkHourPerDay.
Target Platforms: Windows 11, 10, 8, 7 and Linux, MacOS with net8.0, net7.0 or net6.0 installed