remove Identifier completely, update Tests structure

CI/check_format

CI/check_license.py

CMakeLists.txt

Core/include/Acts/Detector/DetectorElementBase.hpp

Core/include/Acts/Utilities/Identifier.hpp

Plugins/CMakeLists.txt

Plugins/DD4hep/CMakeLists.txt

Plugins/DD4hep/include/Acts/Plugins/DD4hep/ActsExtension.hpp

...hep/include/Acts/Plugins/DD4hep/ConvertDD4hepDetector.hpp

...s/DD4hep/include/Acts/Plugins/DD4hep/DD4hepDetElement.hpp

...DD4hep/include/Acts/Plugins/DD4hep/DD4hepLayerBuilder.hpp

...ins/DD4hep/include/Acts/Plugins/DD4hep/IActsExtension.hpp

Plugins/DD4hep/src/ActsExtension.cpp

Plugins/DD4hep/src/ConvertDD4hepDetector.cpp

Plugins/DD4hep/src/DD4hepDetectorElement.cpp

Plugins/DD4hep/src/DD4hepLayerBuilder.cpp

Plugins/Digitization/CMakeLists.txt

...clude/Acts/Plugins/Digitization/CartesianSegmentation.hpp

...tion/include/Acts/Plugins/Digitization/Clusterization.hpp

...on/include/Acts/Plugins/Digitization/DigitizationCell.hpp