[ie] Extract info from <media> elements in SMIL manifest

[seproDev]

IMPORTANT: PRs without the template will be CLOSED

Description of your pull request and other information

Currently, the SMIL parser only extracts media streams from <audio> and <video> elements.
While as far as I can tell not spec compliant, in practice <media> elements are also sometimes used.
Looking around this seems to be something Microsoft likes to do, for example in Windows Media Player Playlists and Windows Media Services.

Needed for proper SMIL parsing in #7790

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
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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 fe9b464

Summary

🎬🛠️🇳🇴

Add support for SMIL files with <media> tags in common.py. This fixes the extraction of some NRK TV videos.

<media> tag found
SMIL extraction improved
Winter of content

Walkthrough

• Support SMIL files with <media> tags by extending the media element XPath (link)