[FEA] Remove numpy dependency

[vyasr]

Is your feature request related to a problem? Please describe.
I have thought about this issue for a while, and in light of #1760 I thought it would be worth raising. Currently rmm uses numpy in exactly one place and it's really just a shortcut to get host buffers with huge pages turned on.

Describe the solution you'd like
We should be able to trivially emulate this behavior by using madvise directly. Then we can remove numpy as a dependency altogether.

[vyasr]

@jakirkham may be able to comment on how useful this optimization even is right now since he added the relevant comment.

[bdice]

I think this is a good idea. I am first working on reducing Numba dependencies in #1760 / #1761. This would be a good follow-up.