Remove unused code

- The old character select scene, which was never shown but loaded
  every character image at startup
- Unused SyncResponse and ProgressResponse classes
- Playlist.set_last_played_answered and select/local-loading code in
  the new character select, none of which were called
- Settings.delete_player_children, identical to delete_children
- An unused variable holding a local file path

new_character_select.gd

@@ -14,7 +14,6 @@ var close_timer: Timer = %CloseTimer
 
 var can_select_character: bool = false
 
-signal character_selected(file_name: String)
 signal new_new_character_selected(file_name: String)
 
 var character: PackedScene = preload("res://character.tscn")
@@ -22,10 +21,6 @@ var character: PackedScene = preload("res://character.tscn")
 func _ready() -> void:
 	close_timer.timeout.connect(_on_close_timeout)
 
-func select_character(file_name: String) -> void:
-	print("select_character")
-	character_selected.emit(file_name)
-
 func _on_close_timeout() -> void:
 	print("_on_close_timeout!")
 	Settings.character_select_open = false
@@ -70,21 +65,3 @@ func _input(event: InputEvent) -> void:
 			if !Rect2(Vector2(0, 0), character_panel.size).has_point(evLocal.position):
 				self.visible = false
 				Settings.character_select_open = false
-
-func load_characters_local() -> void:
-	var characters: DirAccess = DirAccess.open("res://characters/")
-	if characters:
-		characters.list_dir_begin()
-		var file_name: String = characters.get_next()
-		while file_name != "":
-			file_name = file_name.replace('.import', '') # <--- remove the .import
-			if file_name.ends_with(".png"):
-				var texture: Resource = load("res://characters/" + file_name)
-				var texture_btn: TextureButton = TextureButton.new()
-				character_grid.add_child(texture_btn)
-				texture_btn.custom_minimum_size = Vector2(80, 40)
-				texture_btn.ignore_texture_size = true
-				texture_btn.stretch_mode = TextureButton.STRETCH_KEEP_ASPECT
-				texture_btn.texture_normal = texture
-				texture_btn.pressed.connect(select_character.bind(file_name))
-			file_name = characters.get_next()