Add check to detect OOB of Private/Function variables

The following is currently not being caught in GPU-AV and should

```glsl
const float myLut[40] = { /* array initializers... */ };
const int INVALID_LUT_INDEX = 63;

float func(int index) {
return myLut[index];
}

void main() {
/* lots of stuff */
float thing = func(lutIndex); // lutIndex might be INVALID_LUT_INDEX
}
```