[extractor/youtube] Fix parsing comment_count with unit suffix

[nick-cd]

IMPORTANT: PRs without the template will be CLOSED

Description of your pull request and other information

Youtube's extractor can now correctly parse comment count values containing unit suffixes (i.e. K, M, etc.).

Fixes #5849

Template

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[pukkandan]

Pls make sure to manually test both traversal paths. You can test the second path by changing one of the keys in first to intentionally break it.

[nick-cd]

Sure thing :)

I conducted a bit of smoke testing on the same URL as the OP in #5849 (https://www.youtube.com/watch?v=TPKX6K2u8Tc). I shared my results below. (Note: At the time of this writing, the comment counter is around 3.2K.)

First Path Test

The following GIF shows the resultant info dictionary after fetching the comment_count key, following the first expected path:

Second Path Test

In this test, I eliminated twoColumnWatchNextResults from the first path, breaking it. The application now relies on the fallback path to retrieve the comment_count key.

According to these trivial tests, both paths provide the same count information.

Please let me know if this evidence is enough to prove that my patch works.

[pukkandan]

Evidence wasn't necessary 😄. I was just reminding you to test the fallback path

[nick-cd]

Oh, My bad 😄.