sorting of playlist with duplicates and selection selects all duplicates of selection

[ronso0]

Bug Description

• create a playlist with some duplicate tracks, e.g. add TrackA twice
• sort by # position
• select TrackA + x
• sort
• all occurences of TrackA are selected

Desired:

Identify selection by #, not TrackId

Version

2.5-alpha, probably also earlier

OS

No response

[ronso0]

Oh, there's an old TODO

mixxx/src/widget/wtracktableview.cpp

Lines 1339 to 1346 in ada244c

	// TODO(rryan) slowly fixing the issues with BaseSqlTableModel. This
	// code is broken for playlists because it assumes each trackid is in
	// the table once. This will erroneously select all instances of the
	// track for playlists, but it works fine for every other view. The way
	// to fix this that we should do is to delegate the selection saving to
	// the TrackModel. This will allow the playlist table model to use the
	// table index as the unique id instead of this code stupidly using
	// trackid.