venus: conditionally enable async descriptor set allocation

When VK_DESCRIPTOR_POOL_CREATE_FREE_DESCRIPTOR_SET_BIT is not used to
create the pool, set allocation is guaranteed to not return
VK_ERROR_FRAGMENTED_POOL, and we can safely move set allocation to async
after doing resource tracking in the driver.

Enable after fully tested with assert(false) in the failure case.

Tested with:
- dEQP-VK.api.descriptor*
- dEQP-VK.api.object_management.*
- dEQP-VK.binding_model.descriptor*
- dEQP-VK.descriptor_indexing.*

Signed-off-by: Yiwei Zhang <zzyiwei@chromium.org>
Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
Reviewed-by: Ryan Neph <ryanneph@google.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12501>

src/virtio/vulkan/vn_descriptor_set.c

@@ -444,10 +444,15 @@ vn_AllocateDescriptorSets(VkDevice device,
       pDescriptorSets[i] = set_handle;
    }
 
-   result = vn_call_vkAllocateDescriptorSets(dev->instance, device,
-                                             pAllocateInfo, pDescriptorSets);
-   if (result != VK_SUCCESS)
-      goto fail;
+   if (pool->async_set_allocation) {
+      vn_async_vkAllocateDescriptorSets(dev->instance, device, pAllocateInfo,
+                                        pDescriptorSets);
+   } else {
+      result = vn_call_vkAllocateDescriptorSets(
+         dev->instance, device, pAllocateInfo, pDescriptorSets);
+      if (result != VK_SUCCESS)
+         goto fail;
+   }
 
    return VK_SUCCESS;