Reduce Resolver Related Class-Instances

[BenjaminKlatt]

Issue Description

The resolver logic is structured into several classes for better seperation of concerns. However, there are more instances of those classes created as necessary.

Code Review Results

JavaDefaultResolverDelegate

• is used by the IJavaReferenceResolver implementations (e.g. AnnotationAttributeSettingAttributeReferenceResolver)
  They use the deResolve() method only which is thread safe, stateless and process submitted call arguments only.
  => It is an option to let all of them use only a single static instance

IJavaReferenceResolver

The different IJavaReferenceResolver implementations are instantiated by the JavaReferenceResolverSwitch only.
They are all stateless, and all of their setOptions() methods do nothing.
=> All JavaReferenceResolverSwitch instances could use the same resolver instances.

JavaReferenceResolverSwitch

As mentioned before, the resolver in the switch are stateless. The switch's setOptions()-method delegates the options map to the setOptions()-method of the resolvers, which again do nothing.
=> A single instance of the switch would be fine for the whole JaMoPP instance.
=> Within JaMoPP, there are 6 locations creating JavaReferenceResolverSwitch instances. (See screenshot below).

Recommended Adaptation

The locations within the src-gen source directory make all use of the JavaMetaInformation class, which already located in the manually modified source directory. Only JavaResource does create a new switch on it's own. Instead of the JavaResource itself, the JavaSourceOrClassFileResource is used, which is located in java.resource manually adapted source directory.
This allows to modify all 6 locations at already not-generated code locations.

To reduce the instantiation overhead and the memory footprint, these 6 locations should be adapted to request the switch from a factory using the same thread safe singleton.

Optimization Results

With the ArgoUML case study from the SPLevo/KoPL project, for example, the number of delegate instances has been reduced from > 450k (continuously increasing while the case study could not be finished) to 7 constant instances.
Also the switches and Resolvers have been reduced to constant number.