Improves HLS discontinuity sequence handling

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Enhances HLS classic playlist generation and parsing to correctly manage media sequence and discontinuity sequences.

• Introduces dedicated structures (ClassicSegment, ClassicPlaylistWindow, MediaPlaylistState) and helper functions to encapsulate HLS playlist logic, ensuring proper segment handling, duration calculations, and live trimming.
• Updates HLS input parsing to accurately detect and store #EXT-X-DISCONTINUITY and #EXT-X-DISCONTINUITY-SEQUENCE tags, allowing for correct timeline resets and remapping.
• Refactors HLS output generation to utilize the new playlist building utilities, which correctly apply discontinuity logic and media sequence numbering, especially in live streaming scenarios.
• Improves playlist appending functionality by using inspectMediaPlaylist to accurately determine segment counts and media sequences in existing playlists.
• Removes the HEVC HLS blacklist, allowing HEVC streams to be offered in HLS.