Add coco_visualize_videos CLI for rendering video frames with annotations

[Erotemic]

Motivation

• Provide a first-class kwcoco CLI to render video frames (and optional annotation overlays) to disk for inspection and debugging.
• Port the core, generally useful visualization functionality from the legacy dev/to_port/coco_visualize_videos.py while removing project-specific heuristics and deprecated logic.
• Keep a lightweight, robust interface that can operate on small in-memory datasets for CI or local smoke tests.

Description

• Added kwcoco/cli/coco_visualize_videos.py that registers a visualize CLI (alias visualize_videos) implemented with scriptconfig and supporting channel selection, per-video output folders, draw controls (draw_imgs, draw_anns, draw_boxes, draw_segmentations, draw_labels), simple scaling (min_dim, max_dim), and other rendering options.
• Vendored and adapted only two small helper routines from the legacy utilities: perchannel_colorize and ensure_false_color with a short header comment noting the original source and adaptation.
• Registered the new CLI module in the main CLI registry by adding coco_visualize_videos to kwcoco/cli/__main__.py.
• Added a minimal smoke test tests/test_cli_visualize_videos.py that programmatically builds a tiny kwcoco dataset, runs the CLI (__cli__.main(...)) and asserts that visualization images are produced.
• Intentionally omitted/removed: GeoWATCH/SMART-specific heuristics and activity-label assumptions, the legacy animation wrapper, and the select_fixed_normalization fixed-normalization selection and other deprecated flags.

Testing

• Ran the smoke test via python -m pytest tests/test_cli_visualize_videos.py which passed locally.
• The smoke test constructs a tiny dataset (2 frames, 1 video), invokes the CLI with cmdline=False, and asserts that output images are written to the viz folder.
• No additional heavy dependencies or external services were required for the smoke test and it completed successfully.

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Codex Task