[Enhancement] Switch to innertube for the captions - captions do not work on public instances

[unixfox]

Is your enhancement request related to a problem? Please describe.
The current way of retrieving the captions is rate limited by google and captions doesn't work on popular instances.

Describe the solution you'd like
We should switch to the innertube for retrieving the captions because on innertube there is no rate limit (for the moment).

Describe alternatives you've considered

Install and use Invidious locally or switch to a less popular instances from https://instances.invidious.io

Additional context
Related to #2519 and #2565

[syeopite]

Possible solution #2564

[TheFrenchGhosty]

A 20$ bounty has been added to this issue.

Anyone opening a PR fixing this issue, will receive 20$ (in BTC) from the Invidious project.

More details: #1898

[rottenwheel]

I can personally offer $80 worth of XMR on top of the $20 worth of BTC from the Invidious project, to be claimed by whoever opens a PR switching to innertube for captions to work.

Please ping me here, or via Matrix should there be any news or comments; will try to keep an eye open regardless.

[unixfox]

About https://github.com/iv-org/invidious/blob/master/src/invidious/routes/api/v1/videos.cr#L34

timedtext API does now provide links for auto-generated captions. Could this replace the current implement of getting the captions?

[tuxayo]

How does newpipe does it? Is it because it does it directly so it's not rate limited at the expense of a risk of user tracking?

Due to the elapsed time, is this less work-demanding solution worth considering as an alternative? : if proxy is disabled, then do the request for subtitles directly from user's browser.

[tuxayo]

request: rename the issue "Captions don't work on popular instances" or something like that so people can more simply find it. And it's not an enhancement, it's a bug.