[extractor/tencent] Fix fatal metadata extraction

[bashonly]

Update regex pattern, use _search_json to make metadata extraction actually non-fatal

Closes #7177

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 b6f0e8c

Summary

🛠️🆙🚫

Improved Tencent video extraction in yt_dlp/extractor/tencent.py. Used a better JSON parser and updated tests.

Tencent videos
Metadata and formats parsed
Winter tests skipped

Walkthrough

• Simplify metadata extraction using _search_json helper method (link)
• Update md5 values of test cases to match current checksums of downloaded files (link, link)
• Skip test case for unavailable video (link)
• Skip m3u8 format download for encrypted video in test case (link)