Vulkan: Track valid descriptor set layouts Instead of looping through kMaxDescriptorSetLayoutBindings in `DescriptorSetLayoutDesc::unpackBindings` track valid descriptor set layouts in `DescriptorSetLayoutDesc::update` Bug: angleproject:2462 Change-Id: I1ca2ba72875d9306b6059b14cde39c5d16250be6 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5464160 Reviewed-by: Charlie Lao <cclao@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: mohan maiya <m.maiya@samsung.com>