Improve uninitialized_{async_}buffer API (NVIDIA#2713)

This implements some improvements to the buffers.

* We want to be able to convert them if the properties match.
* Add some improvements regarding symbol visibility
* Add a way to grow a vector
* Ensure we can simply swap them

cudax/test/containers/uninitialized_async_buffer.cu

@@ -42,7 +42,7 @@ constexpr int get_property(
 {
   return 42;
 }
-constexpr int get_property(const cuda::experimental::mr::device_memory_resource&, my_property)
+constexpr int get_property(const cuda::experimental::mr::async_memory_resource&, my_property)
 {
   return 42;
 }