Support cue sheets

[selurvedu]

Expected Behavior

Being able to load an album that consists of a single FLAC file and a separate cue sheet that contains the proper album and track metadata.

Current Behavior

The FLAC simply gets loaded as a single long track. No tags or separate tracks are detected.

Possible Solution

¯_(ツ)_/¯

I'm not sure if that's relevant, but Exaile can already handle CDs, and "a cue sheet, or cue file, is a metadata file which describes how the tracks of a CD or DVD are laid out." (quote from Wikipedia). Essentially it's a kind of a playlist.

Upstream GStreamer bugs:
Bug 613319 ->
duplicate of Bug 588269 ->
duplicate of Bug 776613 ->
migrated to https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/213