Reach nodes by unique name instead of long paths

Nodes a script uses through a path of several nodes are marked unique in their
scene and found with %Name. The search list is renamed SearchResults, and the
player row's nodes get their real types.

song_row.gd

@@ -2,10 +2,10 @@ class_name SongRow
 extends PanelContainer
 
 @onready
-var song_list_label: Label = $HBoxContainer/SongListLabel
+var song_list_label: Label = %SongListLabel
 
 @onready
-var song_list_players: HBoxContainer = $HBoxContainer/SongListPlayers
+var song_list_players: HBoxContainer = %SongListPlayers
 
 var song_object: SongObject