Threaded Queue submit with events and fences

This cl does 3 main things:
- It pushes the queue submit operation to its own thread
- It implements events
- It implements fences

Some details:
- Because we can have N async draw operations and we need to signal
  the fence only after all operations are completed, fences have a
  add/done mechanism to allow signaling the fence only when all
  draw operations are completed.
- Device::waitForFences() detects large timeouts to avoid integer
  overflow if now+timeout is bigger than the remaining nanoseconds
  available in a long long.

Bug b/117835459

Change-Id: I2f02c3b4bb9d9ac9037909b02b0601e1bae15d21
Tests: dEQP-VK.synchronization.*
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/29769
Presubmit-Ready: Alexis Hétu <sugoi@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>

src/Vulkan/VkEvent.hpp

diff --git a/src/Vulkan/VkEvent.hpp b/src/Vulkan/VkEvent.hpp
index 4735564..d56da28 100644
--- a/src/Vulkan/VkEvent.hpp
+++ b/src/Vulkan/VkEvent.hpp
@@ -16,6 +16,8 @@
 #define VK_EVENT_HPP_
 
 #include "VkObject.hpp"
+#include <condition_variable>
+#include <mutex>
 
 namespace vk
 {
@@ -34,37 +36,38 @@
 		return 0;
 	}
 
-	bool signal()
+	void signal()
 	{
+		std::unique_lock<std::mutex> lock(mutex);
 		status = VK_EVENT_SET;
-		bool wasWaiting = waiting;
-		waiting = false;
-		return wasWaiting;
+		lock.unlock();
+		condition.notify_all();
 	}
 
 	void reset()
 	{
+		std::unique_lock<std::mutex> lock(mutex);
 		status = VK_EVENT_RESET;
 	}
 
-	VkResult getStatus() const
+	VkResult getStatus()
 	{
-		return status;
+		std::unique_lock<std::mutex> lock(mutex);
+		auto result = status;
+		lock.unlock();
+		return result;
 	}
 
-	bool wait()
+	void wait()
 	{
-		if(status != VK_EVENT_SET)
-		{
-			waiting = true;
-		}
-
-		return waiting;
+		std::unique_lock<std::mutex> lock(mutex);
+		condition.wait(lock, [this] { return status == VK_EVENT_SET; });
 	}
 
 private:
-	VkResult status = VK_EVENT_RESET;
-	bool waiting = false;
+	VkResult status = VK_EVENT_RESET; // guarded by mutex
+	std::mutex mutex;
+	std::condition_variable condition;
 };
 
 static inline Event* Cast(VkEvent object)