Vulkan: Remove EventStage::BottomOfPipe and AllCommands These two StageFlags never being used in VkCmdSetEvent, and should not be used given that these are very strong synchronization. They are removed in this CL. Bug: b/336844257 Change-Id: I68a47a5459dadf56ad5c269ebb3af55887110cc7 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5601811 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Amirali Abdolrashidi <abdolrashidi@google.com> Commit-Queue: Charlie Lao <cclao@google.com>