[Sofa.Simulation.Graph] Remove DAGNode related test files (#5670)

* Merge DAGNode in Node

* Use Node in place of DAGNode in sofa's code.

* Copy past content of DAGNode in Node

* FIXUP forward declaration of BaseMechanicalstate

* FIX Node refactoring invalid merge.

* Clean of the integration of DAGNode into Node

Important things are:
- integration of NODEgetMeshTopologyLink into getMeshTopologyLink

- refactoring of updateContext, updateVisualContext and updateSimulationContext
Some code was shared between them.. so I factorize that into a new method called initializeContexts()

non important things are removal of un-needed static_cast<Node*>

* Add deprecation macro in DAGNode.h forwarding to Node

* Move DAGNode_test DAG_test in Node_test.cpp

* FIX the TEST_F problem

Author: damienmarchal

Sofa/framework/Simulation/Graph/test/CMakeLists.txt

@@ -6,8 +6,6 @@ set(HEADER_FILES
 )
 
 set(SOURCE_FILES
-    DAG_test.cpp
-    Node_test.cpp
     MutationListener_test.cpp
     Node_test.cpp
     Simulation_test.cpp