[Requirement] Custom allocator support for gpu_cache

[mfbalin]

Is your feature request related to a problem? Please describe.
We utilize gpu_cache in the Deep Graph Library project. We would like the gpu_cache to be able to use a custom allocator. That way, we can make it use the pytorch allocator in our project.

[yingcanw]

Thanks for your feedback. We have abstracted the allocator in the latest EmbedCache. You can implement a custom allocator for host and device memory allocation.