nvk: Use max alignment for descriptor pool sizes

nvk: Use max alignment for descriptor pool sizes

Since we only know the number of each descriptor type and not their
groupings, we don't know how alignments will compound.  Figure out the
maximum alignment and then use that for everything to ensure that, no
matter how they're combined, we always have enough room.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24326>