GradientTexture1D/2D changed signal emitted before texture updating which causes issue in certain case

[beicause]

Tested versions

Reproducible in 4.4.dev

System information

Linux - Godot 4.4.dev

Issue description

GradientTexture2D/1D emit changed signal before its texture actually updates, which causes issues in certain case that can't update texture by listen its changed signal. The issue was found in #102028.

Steps to reproduce

The issue occurs if you draw gradient texture in a viewport and only update once.

Attach the follow script to a Node2D, assign a GradientTexture2D/GradientTexture1D to the texture property, then the texture display incorrectly and doesn't update after changing its gradient, unless reload the scene. Instead, assigning a NoiseTexture2D to the texture works well.

@tool
extends Node2D
class_name TestNode2D

@export var texture: Texture2D:
	set(value):
		if texture != null:
			texture.changed.disconnect(queue_redraw)
		texture = value
		if texture != null:
			texture.changed.connect(queue_redraw)
		queue_redraw()
@export var bg_color: Color = Color.WHITE:
	set(value):
		bg_color = value
		queue_redraw()

var size: Vector2i = Vector2i(512, 512)
var vp: RID = RenderingServer.viewport_create()
var vp_canvas: RID = RenderingServer.canvas_create()
var vp_ci: RID = RenderingServer.canvas_item_create()
var update_pending: bool = false
var vp_texture: RID


func _init() -> void:
	RenderingServer.viewport_attach_canvas(vp, vp_canvas)
	RenderingServer.canvas_item_set_parent(vp_ci, vp_canvas)
	RenderingServer.viewport_set_update_mode(vp, RenderingServer.VIEWPORT_UPDATE_ALWAYS)
	RenderingServer.viewport_set_size(vp, size.x, size.y)
	vp_texture = RenderingServer.viewport_get_texture(vp)

func _draw() -> void:
	RenderingServer.canvas_item_clear(vp_ci)
	RenderingServer.canvas_item_add_rect(vp_ci, Rect2(Vector2.ZERO, size), bg_color)
	if texture != null:
		RenderingServer.canvas_item_add_texture_rect(vp_ci, Rect2(Vector2.ZERO, size), texture.get_rid())
	RenderingServer.viewport_set_active(vp, true)
	RenderingServer.force_draw(false)
	RenderingServer.viewport_set_active(vp, false)

	RenderingServer.canvas_item_add_texture_rect(get_canvas_item(), Rect2(Vector2.ZERO, size), vp_texture)

Minimal reproduction project (MRP)

N/A