[extractor/Facebook] fix: Username getting and liveViewerCount

[ringus1]

Description of your pull request and other information

Uploader data is now prioritised to find one with name in it. Falls back to current queries otherwise.
Added optional live_view_count info to metadata too for live videos.

Fixes #3432

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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• Core bug fix/improvement
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[bashonly]

Please review and update code accordingly:
https://github.com/yt-dlp/yt-dlp/blob/master/CONTRIBUTING.md#quotes
https://github.com/yt-dlp/yt-dlp/blob/master/CONTRIBUTING.md#trailing-parentheses

[ringus1]

Done, thanks