add audio_manager and code refactoring

core/audio/settings/settings_menu.gd

@@ -0,0 +1,36 @@
+extends Control
+
+class_name SettingsMenu
+
+@onready var audio_options_container: VBoxContainer = $%AudioOptionsContainer
+@onready var reset_button: Button = $%ResetToDefault_Button
+@onready var close_button: Button = $%Close_Button
+
+func _ready() -> void:
+	reset_button.pressed.connect(_on_reset_to_default_button_pressed)
+	close_button.pressed.connect(_on_close_button_pressed)
+	_refresh_audio_options()
+
+func _get_audio_options() -> Array[AudioOption]:
+	var audio_options: Array[AudioOption] = []
+
+	for child in audio_options_container.get_children():
+		if child is AudioOption:
+			audio_options.append(child)
+
+	return audio_options
+
+func _refresh_audio_options() -> void:
+	for audio_option in _get_audio_options():
+		audio_option.refresh()
+
+func _apply_current_audio_values() -> void:
+	for audio_option in _get_audio_options():
+		audio_option.apply_current_value()
+
+func _on_reset_to_default_button_pressed() -> void:
+	for audio_option in _get_audio_options():
+		audio_option.reset_to_default()
+
+func _on_close_button_pressed() -> void:
+	visible = false