Sneak in a fix for a limited memory leak in Vulkan vertex cache

GPU/Vulkan/DrawEngineVulkan.cpp

@@ -287,6 +287,9 @@ void DrawEngineVulkan::BeginFrame() {
 		vertexCache_->Destroy(vulkan_);
 		delete vertexCache_;  // orphans the buffers, they'll get deleted once no longer used by an in-flight frame.
 		vertexCache_ = new VulkanPushBuffer(vulkan_, VERTEX_CACHE_SIZE, VK_BUFFER_USAGE_INDEX_BUFFER_BIT | VK_BUFFER_USAGE_VERTEX_BUFFER_BIT);
+		vai_.Iterate([&](uint32_t hash, VertexArrayInfoVulkan *vai) {
+			delete vai;
+		});
 		vai_.Clear();
 	}