cubicweb-processing #3574100 add a ProcessingStudy entity type [validation pending]

a study would contain runs and run chains.

prioritynormal
typeenhancement
done in0.6.0
load0.200
load left0.000
closed by#3c3529166435 Add ProcessingStudy entity type and in_study relation
patchProvide an iter_runs method on ProcessingStudy [applied]Implement ITree adapters for Run/RunChain in ProcessingStudy [applied]Add ProcessingStudy entity type and in_study relation [applied]