Vulkan: Bind aligned default uniform buffer size. This makes us let reuse caches more often when uniforms change size slightly. It also simplifies the cache key management. Bug: angleproject:6776 Change-Id: I68ab48ab7761237bb9d28c4a4a88f4fc6e2c5af6 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3439068 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Yuxin Hu <yuxinhu@google.com> Commit-Queue: Jamie Madill <jmadill@chromium.org>