Validate buffer_reference_align is multiple of largest block scalar

inside https://github.com/KhronosGroup/GLSL/blob/main/extensions/ext/GLSL_EXT_buffer_reference.txt it says

> Each buffer reference type has an alignment that can be specified via
the "buffer_reference_align" layout qualifier. This must be a power of
two and be greater than or equal to the largest scalar/component type
in the block.

But the following is valid and should be throwing an error (https://godbolt.org/z/sxs8KP8MG)

```glsl
layout(buffer_reference, buffer_reference_align = 2) buffer Ptr {
uint x;
};
```

(Note - This is currently VU `06314` in Vulkan and I plan to add to `spirv-val` now, but would be nice to have GLSL catch it sooner)

Read the buffer_reference_align rules in extensions/ext/GLSL_EXT_buffer_reference.txt and reproduce the issue with the linked GLSL example. Trace how glslang validates this layout qualifier and compare the result with Vulkan VU 06314 and spirv-val. Done means the invalid alignment is rejected by GLSL validation, with coverage for the reproducer.

Written by the indexing model from the issue text.