[SFD] respect naming guidelines and small const extraction refactor

src/shared/algorithms/Filters/LowPass.h

src/shared/algorithms/SFD/SFDAscent.cpp

src/shared/algorithms/SFD/SFDAscent.h

src/shared/algorithms/SFD/SFDCommon.h

src/shared/algorithms/SFD/SFDDescent.cpp

src/shared/algorithms/SFD/SFDDescent.h