refactor: Setting EntityProperties

• The entity properties are set three times now in the entity producer and partially overwritten. This MR cleans it up, so they are only copied once from the scenario engine input and only additional attributes from the gtgen mantle_ext structs are set.
• Some base attributes are still set for backward-compatibility with the json scenario engine.
• The vertical offset is only set with default values for traffic signs/lights, if no "mount_height" property was set.