Add more detailed messages for unavailable videos

[TotalCaesar659]

Checklist

• I checked, but didn't find any duplicates (open OR closed) of this issue in the repo.
• I have read the contribution guidelines given at https://github.com/TeamNewPipe/NewPipe/blob/HEAD/.github/CONTRIBUTING.md.
• This issue contains only one feature request. I will open one issue for every feature I want to request.

Describe the feature you want

Services have different error messages for unavailable videos. For example:
https://www.youtube.com/watch?v=_PL2HJKxnOM ("Video unavailable. The uploader has not made this video available in your country.")
https://www.youtube.com/watch?v=DP0F9zPxHFQ ("Video unavailable. This video is no longer available because the YouTube account associated with this video has been terminated.")
https://www.youtube.com/watch?v=8VajtrESJzA ("Private video. Sign in if you've been granted access to this video.")
https://www.youtube.com/watch?v=ayI2iBwGdxw ("Members-only content. Join this channel to get access to members-only content like this video, and other exclusive perks.")
https://www.youtube.com/channel/UCQkuGxxd00feSuocVzlf7Pg ("This account has been terminated due to a Trademark claim by a third party.")
https://soundcloud.com/frankvaldorsposaunenband/agent-808 ("This track is not available in your country.")

Is your feature request related to a problem? Please describe it

NewPipe shows the same message "Content unavailable" for all cases:

Additional context

How will you/everyone benefit from this feature?

It will let users to know the reason of the problem for finding a way to solve it.

[PrSunflower]

I agree. Sometimes I am having this error screen because the content isn't available in my country, sometimes I am having the same error screen because the video doesn't exist anymore.

[litetex]

I think this is fixed:

• Not working in your country
  
• Video unavailable due to terminated account
  
• Private video
  
• Members-only content
  
• Channel - Account terminated
  
• https://soundcloud.com/frankvaldorsposaunenband/agent-808 works in my country 😆