[threads] Add extractor (Threads.net)

[renandecarlo]

Description of your pull request and other information

This is a basic threads.net extractor. It's able to retrieve post's metadata, videos and thumbnails. Both from single and multiple (carousel) media posts. It does not have a login feature for now.

Note this is my very first python anything. Please be merciful.

Fixes #7523

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)