zink: abstract zink_get_resource_usage() and move it to be internal

zink: abstract zink_get_resource_usage() and move it to be internal

I'll be rewriting how resource tracking works, so abstracting it and removing
direct uses is going to reduce the chances of breaking things as well as code churn

plus it's a bit easier to use

downside is that until that rewrite happens, this will be a (very small) perf hit and
there's some kinda gross macros involved to consolidate code

Reviewed-by: Dave Airlie <airlied@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9626>