Philippe 20/03/2024: adapt namelist to use backup frequencies and ensure backup times are multiple of timestep

Conflicts:
	src/ARCH_SRC/CPL_WAVE/MNH/ground_paramn.f90
	src/ARCH_SRC/CPL_WAVE/MNH/ini_modeln.f90
	src/MNH/default_desfmn.f90
	src/MNH/goto_model_wrapper.f90
	src/MNH/ground_paramn.f90
	src/MNH/ini_lb.f90
	src/MNH/ini_modeln.f90
	src/MNH/modeln.f90
	src/MNH/read_exsegn.f90
	src/MNH/read_field.f90
	src/MNH/write_aircraft_balloon.f90
	src/SURFEX/ch_init_depconst.F90
	src/SURFEX/ch_init_emissionn.F90
	src/SURFEX/ch_init_snapn.F90
	src/SURFEX/init_surf_atmn.F90
	src/SURFEX/writesurf_snapn.F90