hdl/*: fix monit stage position attenuation
models/ddc_bpm_476_066.mdl: update sysgen model
models/ddc_bpm_476_066_hw_cosim.mdl: update hw cosim sysgen model
models/*: add backup models (will be deleted)
models/round_gain.mdl: add custom subsystems
models/tests/*: update monit test model