[MediaCCC] Fix regressions and improve MediaCCCLiveStreamKioskExtractor

[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.

Changes

• Fix wrong ListLinkHandlerFactories for kiosks. Regression introduced in #1082. I checked for similar regressions, but did not find any.
• Live stream kiosk: detect pause "talks" segments. Add and improve tests for MediaCCCLiveStreamKioskExtractor:
  • test stream items if a live stream is running
  • use mock tests to check live talk extraction and testing conferences

To Do

• [x] Make MediaCCCLiveStreamListExtractorTest.[PreparationTest|LiveConferenceTest] always use mocks.