BaseJobDescriptionModel uses Operations inappropriately

[chrisburr]

The new BaseJobDescriptionModel uses Operations() as part of the definition of a class, e.g.

DIRAC/src/DIRAC/WorkloadManagementSystem/Utilities/JobModel.py

Line 18 in 9475045

cpuTime: int = Operations().getValue("JobDescription/DefaultCPUTime", 86400)

This doesn't do what is expected as it is evaluated during the import of the file.

The simple solutions would be to use default_factory with Operations() however this relies on global state that isn't present in DiracX so it's not a good idea. The best solution probably requires a bit more thought.