Vulkan: Keep referenced pipeline libraries alive As required by the spec, it's not enough to keep the linked pipeline alive. With this change, the serials of the invidual libraries are updated every time the serial of a linked pipeline is updated. Bug: angleproject:7369 Change-Id: Iedc98a427d988d00b4e8745964d9827fdf51ea7f Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4098744 Reviewed-by: Charlie Lao <cclao@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>