[extractor/bilibili] Support festival videos

[qbnu]

IMPORTANT: PRs without the template will be CLOSED

Description of your pull request and other information

Adds support for "festival" videos on Bilibili. These videos have a different layout and require an API call to get download links.

Fixes #6138

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

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• Fix or improvement to an extractor (Make sure to add/update tests)
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• Core bug fix/improvement
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