Fix GPU Buffer Validation Settings

The `VK_LAYER_GPUAV_ACCELERATION_STRUCTURES_BUILDS` and `VK_LAYER_GPUAV_RAY_TRACING_BUFFERS_CONSISTENCY` settings currently don't make sense.

The "seem" to be part of `VK_LAYER_GPUAV_BUFFERS_VALIDATION`... but also not

1. In the logic

```c++
if (!buffers_validation_enabled) {
gpuav_settings.SetBufferValidationEnabled(false);
} else {
// here
}
```

they are not checked,

2. In `SetBufferValidationEnabled` they are set? (also `SetBufferValidationEnabled` probably should just be `DisableBufferValidation` at this point)

3. `IsBufferValidationEnabled` doesn't set it (which seems correct)

4. The top of `layer_options.cpp` they are grouped with `VK_LAYER_GPUAV_BUFFERS_VALIDATION` which is misleading

... basically @arno-lunarg not sure where these settings fit, so we should make things consistent before adding more settings around Ray Tracing