Add HeightMapShape3D update with Image data

[smix8]

Adds HeightMapShape3D update with Image data.

Populating height values in a heightmap collision from an image file is a common use.
It shouldnt be required that users need to read large image data arrays with slow scripts to achieve this basic thing.

So what this pr does is add update_map_data_from_image() as a new function to HeightMapShape3D.

The function allows a single component black&white Image in format FORMAT_RF (32 bit) or FORMAT_RH (16 bit) or FORMAT_R8 (8 bit) as input and to define a minimum and maximum height range. The image pixel values read in 0.0 to 1.0 range are then remapped to those values.

The code for this was actually found in part on the PhysicsServer3D as more or less dead-code not reachable by users. It also makes far more sense to have this functionality on the collision shape directly to update the map_data. This data array is commonly used for other related stuff, like creating procedual meshes from the heightmap data.

Full usage example to create heightmap collision from an image file:

extends Node3D

func _ready() -> void:
    var heightmap_texture: Texture = ResourceLoader.load("res://heightmap_image.exr")
    var heightmap_image: Image = heightmap_texture.get_image()
    heightmap_image.convert(Image.FORMAT_RF)

    var heightmap_shape: HeightMapShape3D = HeightMapShape3D.new()
    var height_min: float = 0.0
    var height_max: float = 10.0
    heightmap_shape.update_map_data_from_image(heightmap_image, height_min, height_max)

    var static_body: StaticBody3D = StaticBody3D.new()
    var collision_shape: CollisionShape3D = CollisionShape3D.new()
    collision_shape.shape = heightmap_shape
    static_body.add_child(collision_shape)
    add_child(static_body)

[Redwarx008]

Great feature, it would be even better if the HeightMapShape3D could be updated partially from the height map image.

[smix8]

Added error msgs and support for the lower precision formats Image::FORMAT_RH and Image::FORMAT_R8.

@Redwarx008 Partial updates (and reads) should be also made available, not only for the image but also for the normal byte array. I will see what I can do but that deserves its own pr.

[Calinou]

Tested locally (rebased on top of master 29b3d9e), it works as expected.

Testing project: test_pr_87889.zip

[Calinou]

I wonder if this code can be moved below the switch statement, and have the default branch use return instead. This way, we can avoid repetition in the 2 branches below.

[akien-mga]

Not easily, the way pixel_value is calculated depends on the data type, and it needs to be calculate in the for loop for each index.

[akien-mga]

Thanks!