playlist: NewPipe is adding same video on a playlist multiple times

[ghost]

Checklist

• I am using the latest version - 0.21.12
• 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 bug. I will open one issue for every bug report I want to file.

Steps to reproduce the bug

• play a video and add it to a playlist
• try adding it again

Actual behavior

Same video is added to the playlist again, creating a duplicate

Expected behavior

Tell that the video is already on that playlist and don't add a duplicate.

Screenshots/Screen recordings

Logs

Device info

• Android version/Custom ROM version: 10 Go
• Device model:

[SameenAhnaf]

Duplicate of #5558.