Remove unused .h files

legacy/simulation_oop/core_operations.h

legacy/simulation_oop/custom_operation.h

legacy/simulation_oop/operation.h

legacy/simulation_oop/signal_flow_graph.h

legacy/simulation_oop/simulation.h

legacy/simulation_oop/special_operations.h

src/algorithm.h

src/debug.h

src/number.h

src/simulation.h

src/simulation/compile.h

src/simulation/format_code.h

src/simulation/instruction.h

src/simulation/run.h

src/simulation/simulation.h

src/span.h