vulkan: delay pipeline layout destroy until all referent pipelines gone

bug: https://bugs.fuchsia.dev/p/fuchsia/issues/detail?id=51867

Works around

bug: 155664177
Change-Id: I1955c01daff9115d4e6a10f4104f11679822eb73
1 file changed
tree: f3448fa361f469d08a61f6de2a3b10a747849630
  1. registry/