Add `available_device_memory` to fetch free amount of memory on a GPU

[galipremsagar]

Description

This PR adds get_free_device_memory that returns free GPU memory necessary for https://github.com/rapidsai/cudf/pull/15628

Checklist

• [x] I am familiar with the Contributing Guidelines.
• [x] New or existing tests cover these changes.
• [x] The documentation is up to date with these changes.

[galipremsagar]

/merge