ENH: use iterative cost functions

src/MRIBuilder.jl

src/build_sequences.jl

src/components/instant_gradients.jl

src/components/pulses/composite_pulses.jl

src/components/pulses/constant_pulses.jl

src/components/pulses/instant_pulses.jl

src/components/pulses/sinc_pulses.jl

src/components/readouts/ADCs.jl

src/containers/alternatives.jl

src/containers/base_sequences.jl

src/containers/building_blocks.jl

src/parts/helper_functions.jl

src/parts/spoilt_slice_selects.jl

src/parts/trapezoids.jl

src/variables.jl