Show instruction count of compiled shader

[priyansh0219]

It would be good if godot showed the instruction count of shader just like in ue5 so we can better optimize it.

[Calinou]

When using Vulkan-based renderers, Godot compiles the GLSL shader (which is generated from the Godot shader language) into SPIR-V. This SPIR-V (which is an intermediate representation) is then compiled into the binary shader expected by the graphics driver. See RenderingDevice's shader_compile_spirv_from_source() and shader_compile_binary_from_spirv()).

The question is, at which stage should we report instruction count (and where can we get it easily in a way that can be exposed in the editor)?

Note that the Compatibility rendering method (which uses OpenGL) doesn't use SPIR-V. It goes from GLSL to binary shader directly.