overlays: array of struct instead of array of individual members

src/cats/actions/action_overlay_update.c

src/cats/configuration/load_configuration_overlays.c

src/cats/configuration/print_configuration.c

src/cats/inline_overlays.h

src/cats/overlays/overlay_exclusion.c

src/cats/overlays/overlays.c

src/cats/overlays/overlays.h

src/cats/populations/carrying_capacity.c

src/cats/stats/grid_stats.c