feat(tracks): probe dv tracks for hdr10+ and list them as DV+HDR10P

A DV track that carries HDR10+ keeps its DV range and gets Video.hdr10plus, sent in the REST track JSON and to remote clients.

docs/dev/rest-api/endpoints.md

@@ -332,7 +332,7 @@ When you give both `season` and `episode`, the server combines them into a `"{se
           "bitrate": 8000, "bitrate_bps": 8000000, "width": 3840, "height": 2160,
           "resolution": "2160p", "fps": "24", "range": "HDR10",
           "range_display": "HDR10", "scan_type": null, "closed_captions": [],
-          "dv_compatible_bitstream": false, "language": "en", "is_original_lang": true,
+          "dv_compatible_bitstream": false, "hdr10plus": false, "language": "en", "is_original_lang": true,
           "name": null, "needs_repack": false, "edition": [], "data": null,
           "drm": [], "descriptor": "DASH"
         }

docs/reference/configuration/download.md

@@ -379,6 +379,10 @@ reads the first fragment of HEVC HDR10 tracks from DASH, HLS fMP4 and one-file s
 whose first frame carries HDR10+ (SMPTE ST 2094-40) metadata becomes `HDR10P`. Then `-r HDR10P`,
 `--list` and [`--generate-dv`](../../guide/downloading.md#dolby-vision-from-hdr10) use it.
 
+unshackle also probes HEVC Dolby Vision tracks. A DV track that carries HDR10+ keeps its `DV`
+range, so `-r DV` and `-r HYBRID` select it as before, and `--list` shows it as `DV+HDR10P`. The
+HDR10 tracks and the DV tracks of a title are sampled as two separate sets.
+
 When two HDR10 tracks have the same resolution, they can be an HDR10 encode and an HDR10+ encode
 side by side, so unshackle probes every track. When each track has its own resolution, unshackle
 probes the two highest and the two lowest bitrates first: