Rewrite OnDemandKorea Extractor

[seproDev]

IMPORTANT: PRs without the template will be CLOSED

Description of your pull request and other information

Requires Python 3.8 due to the use of the walrus operator.
Not entirely sure if the series check inside traverse_obj is the most elegant way to write this.
Both were addressed in review.

Fixes #8374

Template

Before submitting a pull request make sure you have:

• At least skimmed through contributing guidelines including yt-dlp coding conventions
• Searched the bugtracker for similar pull requests
• Checked the code with flake8 and ran relevant tests

In order to be accepted and merged into yt-dlp each piece of code must be in public domain or released under Unlicense. Check all of the following options that apply:

• I am the original author of this code and I am willing to release it under Unlicense
• I am not the original author of this code but it is in public domain or released under Unlicense (provide reliable evidence)

What is the purpose of your pull request?

• Fix or improvement to an extractor (Make sure to add/update tests)
• New extractor (Piracy websites will not be accepted)
• Core bug fix/improvement
• New feature (It is strongly recommended to open an issue first)

Copilot Summary

🤖 Generated by Copilot at 19aa313

Summary

🆕🔄✨

Add a new extractor class for OnDemandKorea programs and rewrite the existing extractor class for OnDemandKorea videos. The new classes use a different API endpoint, support more features and formats, and handle errors better. Update the tests and the import statement in _extractors.py accordingly.

ondemandkorea.py
New API, more features
Autumn of improvement

Walkthrough

• Import and register new extractor class for OnDemandKorea programs (link)
• Rewrite extractor classes for OnDemandKorea videos and programs using a different API endpoint and URL pattern (link)