[common] (viewer) Add viewer class, and use it for robots demos

common/polystar/common/view/blend_object_on_image.py

common/polystar/common/view/blend_text_on_image.py

common/polystar/common/view/cv2_results_viewer.py

...polystar/common/view/plt_display_image_with_annotation.py

common/polystar/common/view/plt_display_image_with_object.py

common/polystar/common/view/plt_results_viewer.py

common/polystar/common/view/results_viewer_abc.py

robots-at-robots/research/demos/demo_infer.py

robots-at-robots/research/demos/demo_pipeline.py

robots-at-robots/research/demos/demo_pipeline_camera.py