Draft: gsk: Fix bug regarding fixed-size array declarations in GLSL ES

Fixes #5811 (closed)

Fixes to those codes that are in line with the GLSL ES specification that the array size must be written after the variable name.

I'm not familiar with OpenGL so I don't know if this is the best fix, but at least the shaders in gtk4-demo that were crashing before now work. There are some shaders that are not compiling as you can see in the screenshot, but I have a feeling that this is the problem.