AudioStreamPlayer3D autoplay does not work after AudioStreamPlayerInternal refactor

[aaronfranke]

Tested versions

4.3-dev master as of today 51991e2 (happens on any commit after #87061)

System information

macOS 14.2.1, Apple M1 Pro

Issue description

AudioStreamPlayer3D's autoplay property does not work as of #87061

The ENTER_TREE notification is never run for the 3D node:

void AudioStreamPlayerInternal::notification(int p_what) {
	switch (p_what) {
		case Node::NOTIFICATION_ENTER_TREE: {
			print_line("enter tree");

The audio plays correctly if I use the remote scene tree to set playing to true.

Commits before #87061 work fine, and if I revert #87061 it works fine.

Steps to reproduce

1. Open the minimal reproduction project.
2. Set different audio player nodes as autoplay.
3. Observe the following:
   • In master after 87061, AudioStreamPlayer3D autoplay does not work, but it works for 0D and 2D.
   • Before 87061, autoplay works on all players: 0D, 2D, and 3D.

Minimal reproduction project (MRP)

AudioStreamPlayerAutoPlayBroken.zip