Vulkan: SharedFence is now AtomicSharedPtr<RecyclableFence> This is the preparation before the next CL: Vulkan: Improve CommandQueue concurrency crrev.com/c/angle/angle/+/6067346 The `SharedFence` was replaced with `AtomicSharedPtr<RecyclableFence>` because previous implementation reference counting is not thread safe which will be required in the next CL, where fence may be released during unlocked wait or release commands using different mutexes. Additionally cleanup unnecessary use of `vk::` namespace. Bug: b/362604439 Change-Id: Icc61dc093ba0a1e350f1a02eb1ba209a2c58c603 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6074131 Reviewed-by: Charlie Lao <cclao@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Igor Nazarov <i.nazarov@samsung.com>