Clean up Pass by reference & const correctness

[TokisanGames]

Description

Some functions pass various Godot objects by reference, others not. Here's a sizeof comparison, showing which objects are worth passing by reference. By reference passes a uint64_t 8 byte pointer.

Type, sizeof(type)

• Transform3D: 48
• AABB: 24
• Variant: 24
• Color: 16
• Vector3: 12
• Vector2, Vector2i: 8
• Ref, String, Array, Dict, RID: 8

There are also many uses of const Ref<Terrain3DStorage> & in parameters, when the ref is already a reference pointer.

Tasks:

• Standardize on everything >4 bytes passing by const & for 32-bit systems
• Add const to parameters where missing and appropriate

Started on a PR but then accidentally pushed it into main, so WIP at 24008a6137c38cd00156f3efbda9626413eae5a9

[TokisanGames]

@mihe I noticed all throughout Godot-jolt, you pass const RID&. But RID is already 8 bytes, and it copies over the same RID, so the use of & seems redundant. Is there another reason you use it?

[mihe]

The generated (C++) code for RID scared me enough to stop passing it by-value. I haven't looked at the generated assembly code for it, but seeing as how the copy constructor has to go through the bindings means that it'll never get inlined/optimized away, so struck me as quite expensive. Its move constructor is also not defined in the header file, so you're sort of relying on LTO/LTCG to optimize out that function call.

But for the most part I try to keep my codebase mostly Godot-like (with a lot of arbitrary exceptions) and Godot passes RID by-ref everywhere, presumably because of 32-bit platforms.

[TokisanGames]

Thanks @mihe