inclusiveEndDates should respect input date granularity

[VladimirAlexiev]

Describe the bug
inclusiveEndDates (introduced by #872) works only at the granularity of Day.

• However, allow relative dates in Gantt (eg m1,m2,m3) #2850 shows an example of scheduling in Months (often used in Horizon Europe research proposals).
• In other situations one may want to schedule in Hours

To Reproduce
See this example

gantt
    dateFormat  YYYY-MM
    inclusiveEndDates
    section Section
    Should be 2m long  : 2023-10, 2023-11
    Is 2m long        : 60d

Expected behavior
Both tasks should be 2m long. But the first one is only 1m+1d long (from 2023-10-01 to 2023-11-01 inclusive).