Move #all[EntityType] methods from MooseAbstractGroup to lower in the hierarchy

[ClotildeToullec]

These methods are not metamodel-specific, so they do not always make sense when sent to a model:
myJavaModel allModelNamespaces, myJavaModel allNamespaces

They are not EntityGroup-specific, so they don't always make sense when sent to a group:
aFamixMethodGroup allClasses

Should these methods be generated for each Famix[Language]Model?
Should the relevant methods be added to each Famix[EntityType]Group?

[badetitou]

I think the point is when you have a group with multiple kinds of entity inside, you can filter quickly.
I may have some usecase, but not sure, and in general I prefer the usage of allWithType

Still, do we have a problem with the current implementation?
If not, I propose only to improve the generator to add some methods on Famix[Language]Model

IMO, it should be implemented as withGroup and withTesting modularMoose doc, so nothing is generated except if explicitly declared in the generator.

Also, if we start adding more stuff than withTesting, withGroup, now, with withAllOfTypeMethod, I suggested to create a method inside the generator

• defineClasses
• defineHierarchy
  ...
• defineHelpers?

[NicolasAnquetil]

Initializing all these cached groups takes a perceptible time when loading a model