[FEA]: Multi-Device Memory Resource and Buffer Example

Implement a memory resource type holding a resource per device (optionally a pool per device, exposed as shared resource). Resource passes allocation to device pool/resource based on stream/device. Implement `multi_device_async_buffer` inheriting from `async_buffer` and holding the resource. Show how `switch_stream` reallocates/copies memory asynchronously to a new device if needed.