Major refactor of PMT's core and all backends

.gitlab-ci.yml

CMakeLists.txt

amdsmi/AMDSMIImpl.cpp

amdsmi/AMDSMIImpl.h

bin/main.cpp

cmake/modules/AddSensor.cmake

common/CMakeLists.txt

common/Exception.h

common/PMT.cpp

common/PMT.h

common/State.cpp

common/State.h

common/Timestamp.h

common/cpu.h

cray/Cray.cpp

dummy/Dummy.cpp

dummy/Dummy.h

likwid/LikwidImpl.cpp

likwid/LikwidImpl.h

nvidia/NVIDIA.cpp