Add Texture2D and Texture3D icons

[MewPurPur]

Texture2D and Texture3D have quite established shapes, so I think we should make use of it for the abstract classes, to help with visual grepping when they're folded in the Create dialog.

[YuriSizov]

Could you force-push your PR so the CI runs again?

[Calinou]

Looks good to me. Note that Texture2DRD and Texture3DRD are missing icons (RD stands for RenderingDevice):

[MewPurPur]

Godot has R-dimensional textures now? :O

No idea what these are or what would work for them. Hmu if you have ideas or if you can suggest something.

[Riteo]

@MewPurPur

Godot has R-dimensional textures now? :O

RD stands for RenderingDevice as @Calinou pointed out.

Based on the docs it looks like they reference a texture created directly on the RenderingDevice, so it's some low-level thing I suppose.

I'm not really sure how that could be conveyed. Maybe you could draw "RD" inside, somehow pair it to a GPU symbol (I think that'd be a fair generalization) or maybe an arrow, to represent that it's actually somewhere else?

[MewPurPur]

I was making a joke 😓

The GPU thingy sounds interesting, but I realized we don't have any kind of common convention for it. CPU has one (on CPUParticles) which would've been cool, but... yeah it's an association with CPUs, I think it wouldn't be ugly, but it's wrong in a way that would irk people easily. GPUs don't seem to have any conventional icons people would find familiar as far as I see. So as I see it, I'll have to think of something more abstract to do for it and its 3D analogue.

[YuriSizov]

Thanks!

[YuriSizov]

Cherry-picked for 4.2.2.