glsl: move stream layout qualifier validation

glsl: move stream layout qualifier validation

We are moving this out of the parser in preparation for compile
time constant support.

The reason a validation function is used rather than an apply
function like what is used with bindings is because glsl allows
streams to be defined on members of blocks even though they must
match the stream thats associated with the current block, this
means we need access to the value after validation to do this
comparision.

V2: Fix typo in comment (Emil)

Reviewed-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>