Add toString for BeforeEvaluateAllEventImpl and AfterEvaluateAllEventImpl

the idea of this PR is to provide toString method to those two Events.

Here is the template of the implementation :

"....{ modelNamespace=" + modelNamespace + ", modelName=" + modelName + "}"

this simple template avoid to get this kind of log "org.kie.dmn.core.impl.AfterEvaluateAllEventImpl@33c9c80e"