Cubemaps are considered layered and to create a texture view the texture
mustn't be a layered texture, resulting in cubemaps being bound as
cubemap arrays. To fix this issue this commit introduces an extra
surface parameter called "is_array" and uses this to query for texture
view creation.
Now that texture views for cubemaps are actually being created, this
also fixes the number of layers created for the texture view (since they
have to be 6 to create a texture view of cubemaps).
In some constexpr functions, msvc is building the LUT at runtime
(pushing each element onto the stack) out of an abundance of caution. Moving the
arrays into be file-scoped constexpr's avoids this and turns the functions into
simple look-ups as intended.
