Refactor Stream to enum with typed variants (Video, Audio, Subtitle)

Each stream type has only its relevant fields. No more HDR on audio
or channels on video. Added SubtitleStream.forced field (TODO: parse).
Removed display helpers from lib (belongs in CLI).

src/lib.rs

@@ -87,5 +87,6 @@ pub use profile::{DriveProfile, Chipset};
 pub use platform::{Platform, DriveStatus};
 pub use scsi::ScsiTransport;
 pub use speed::DriveSpeed;
-pub use disc::{Disc, DiscFormat, Title, Clip, Stream, StreamKind, Codec, HdrFormat, ColorSpace,
+pub use disc::{Disc, DiscFormat, Title, Clip, Stream, VideoStream, AudioStream, SubtitleStream,
+               Codec, HdrFormat, ColorSpace,
                Extent, ContentReader, AacsState, KeySource, ScanOptions};