Dolibarr 21 Compatibility

[vdegrandpre]

Dolibarr 21 introduces the billable field in the Task object.

Therefore, Timesheet module need to adapt to use the new task attribute instead of the extra attribute the module adds.
Also, the module must migrate all the extrafields billable data to the new task attribute when a migration to 21 occurs.

[vdegrandpre]

Dolibarr/dolibarr#30092

[vdegrandpre]

Working on it.

[delcroip]

this should simply replace 'invoiceable'

[delcroip]

I did a new branch but the migration of the invoicable field need to be done

[vdegrandpre]

Désolé du délai. Mon équipe est là-dessus aujourd'hui.