Instead of having two different helpers, delete the pipeline_cache ones.
Also, instead of manually handling the cache == NULL case in every
vkCreateFooPipelines call, handle it inside the helpers. This means
that BLORP can use them too by passing cache=NULL.
Reviewed-by: Connor Abbott <cwabbott0@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13184>