Vulkan: Restrict VkEvent to TBRs VkEvent has much bigger overhead. Until we know that it helps desktop GPUs, we restrict it to TBRs. Also enabled for SwiftShader so that we get more test coverage in bots. Bug: b/336844257 Change-Id: Ie1859a515c9969ca37f07eae0ff729dd934eb26e Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5714391 Commit-Queue: Charlie Lao <cclao@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>