* Make AudioStreamPolyphonic not requre a polling thread (simpler, faster)
* Improve error reporting in AudioStreamPlayer*::get_stream_playback() error reporting to improve usability.
* This new audio stream allows to play multiple sounds and control them over time from code.
* It greatly simplifies tasks such as generative music (music generated from code) or audio.
This new type of stream was added with the goal of fixing audio blending in AnimationPlayer and AnimationTree, but can be used by others for their regular audio needs.
Does not fix anything currently, but should help implement #69758 properly.
Some demo code of how to use this:
```GDScript
var player = $SomeNode as AudioStreamPlayer
player.stream = AudioStreamPolyphonic.new()
var playback = player.get_stream_playback() as AudioStreamPlaybackPolyphonic
var id = playback.play_stream(preload("res://Clip1.ogg"))
await get_tree().create_timer(1).timeout
playback.set_stream_volume(id,-12) # Set volume to half after one second
await get_tree().create_timer(2).timeout
var id2 = playback.play_stream(preload("res://Clip2.ogg")) # 2 seconds later, start another clip
await get_tree().create_timer(1).timeout
playback.stop_stream(id) # 1 second later, kill the first clip
playback.set_stream_pitch_scale(id2,1.5) # Make the second clip go 50% faster
```
* Works for binary and text files.
* Makes EditorQuickOpen work with custom resources again.
* Information is cached and easily accessible.
Properly fixes#66179. Supersedes #66215 and supersedes #62417
**WARNING**: This required breaking backwards binary compatibility (.res and .scn files). Files saved after this PR is merged will no longer open in any earlier versions of Godot.
This PR is a follow up to #64092, which fixed important issues but it was implemented in an overly complex and inefficient way (because it forced the default code path to always go through string operations).
This cleans up all the shader parameter code.
This fixes#54336. Also fixes#56219 because, as the new code never queries the RenderingServer on load, potential deadlocks are avoided.
**NOTE**: materials saved between #62972 and #64092 will no longer work and will need to be resaved in an earlier version.
- Make all margin properties follow the same naming convention (their getter and setter too).
- Remove a virtual counterpart of `get_style_margin` from API.
- Allow to override `get_minimum_size` from scripting and remove `get_center_size`.
