Semantic segmentation plugin

[pepisg]

Sample yaml config

semantic_segmentation_layer:
        plugin: nav2_costmap_2d::SemanticSegmentationLayer
        enabled: True
        segmentation_topic: "/semantic_segmentation/segmentation/image_raw"
        pointcloud_topic: "/camera/depth/color/points"
        max_obstacle_distance: 3.5
        min_obstacle_distance: 0.5
        class_types: ["traversable", "warning", "danger"]
        traversable:
          classes: ["Sidewalk"]
          cost: 0
        warning:
          classes: ["Pads"]
          cost: 90
        danger:
          classes: ["Grass", "Other"]
          cost: 254
      always_send_full_costmap: True