[SoundCloud] Add support for comment replies

[TobiGr]

• [x] I carefully read the contribution guidelines and agree to them.
• [x] I have tested the API against NewPipe.
• [x] ~I agree to create a pull request for NewPipe as soon as possible to make it compatible with the changed API.~
  Not needed. Is done in https://github.com/TeamNewPipe/NewPipe/pull/9410

Follow up on #936 and #941

To Do:

• [ ] self review
• [x] finish some comments
• [x] checkstyle
• [ ] Fix getting all comments & replies: caching problems after getting replies leading to wrong comments when getting the next page for the original comment tree.